886 lines
50 KiB
Plaintext
886 lines
50 KiB
Plaintext
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ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
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º º
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º The Quest for the º
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º Ultimate Display System º
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º º
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º by º
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º Steve Gibson º
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º GIBSON RESEARCH CORPORATION º
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º º
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º Portions of this text originally appeared in Steve's º
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º InfoWorld Magazine TechTalk Column. º
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º º
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ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
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I remember those simple days not so long ago when a purchaser of
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a brand new IBM Personal Computer had only one choice to make
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when it came to choosing the display system for his computer.
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Blessedly, the only choice to be made back then was between
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either a monochrome display and adpater, the so-called MDA
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solution, or a color screen and adapter, and CGA route. Needless
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to say, things are not so simple or straightforward these days!
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There are so many choices and options open to a purchaser or
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upgrader of a PC that I'd be crazy to even ATTEMPT to offer any
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clarification or guidance.
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Okay, so call me crazy. It's time to choose the display
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subsystem for Steve's Dream Machine and I've got some real
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surprises in store for you this time! I've spent most of the
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past six weeks (when I haven't been reconfiguring my system
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between VM/386, Desqview, and Omniview) researching, probing,
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and digging for the best possible contemporary display solution
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for the least possible money.
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Surprisingly, my research has uncovered some truly startling
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facts which I'll be sharing through the next few weeks as we
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explore THE DISPLAY SYSTEM FOR STEVE'S DREAM MACHINE. We'll see
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things like why the new 16-bit display adapters are generally
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not worth a dime more than their older 8-bit predecessors, how
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few, if any, VGA adapters on the market are REALLY register
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level compatible, and what risk that represents in light of
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IBM's unknowable future plans. We'll see what extra display
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memory DOESN'T buy for you because many of the manufacturer's
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device drivers don't even use it, why the highest resolution
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modes can be much more trouble than they're worth, and what NOT
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to pay for a great high resolution display.
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Given the incredible variety of available choices (not at all
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like in the old days) it may surprise you to know that I have
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found ONE set of choices which delivers far more bang for the
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buck than any other! In order to give these conclusions a proper
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perspective, let's first step back for a moment to review the
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technological fundamentals and constraints which give our
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decision meaning. Then we'll see where we've been and where
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we're going.
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No matter what style of display screen and interface adapter is
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in use, several fundamentals always apply. In the first place,
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the image displayed by a CRT screen is not at all the static
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image which it appears to be. In fact, there's never really an
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image being displayed on the screen at all! If you were to
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photograph a computer display screen with a high speed camera
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you'd only see a single bright dot of light rather than an
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entire image.
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The illusion of a screen full of information is created with the
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aid of some incredible technology. The screen is actually
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painted by a single madly whizzing dot of light which traces
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successive horizontal lines across and down the face of the
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display tube. When I say "madly whizzing" I'm not exaggerating
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because a typical CRT screen paints horizontal scan lines on its
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face at the rate of 350,000 inches per second, which is 20,000
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miles per hour! This furious speed is required in order to fool
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our eyes into believing that the entire image is being
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continuously displayed when in fact it's mostly NOT being
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displayed!
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A typical display screen consists of about 450 of these
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horizontally scanned lines, each of which must be redrawn or
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"refreshed" at least every sixtieth of a second. This means
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scanning across 27,000 lines per second, every second. If this
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is not done our eye will perceive that the lines are not being
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continuously illuminated and the illusion we've tried so hard to
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achieve will fail.
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As the single dot of light traces its furious course it changes
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color thus tracing out the full screen image which is stored in
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the display adapter's DISPLAY REFRESH MEMORY. On a monochrome
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screen which is limited to displaying a single color, the dot of
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light varies in brightness only, whereas a color display system
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allows the dot's instantaneous color to be varied as well.
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So we're left with a number of important concepts: In order to
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eliminate the overall "refresh flicker" of a display screen, the
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entire screen must be redrawn or repainted approximately 60
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times each second. Since the scanning dot traces lines from left
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to right as it moves more slowly vertically from the top of the
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screen down, the downward motion is referred to as the screen's
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Vertical Refresh Frequency and the very rapid horizontal left to
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right scanning is referred to as the display's Horizontal
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Refresh Rate.
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The Display System Adventure Continues
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So we've seen that the display screens of our computers rely
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entirely upon our eye's persistence of vision to assemble the
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illusion of an image on the screen. Each dot which composes the
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display must be redrawn, or refreshed, at least sixty times each
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second in order to appear continuously illuminated. Now we'll
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examine the evolution of our display screens, giving some
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perspective to where we've been and where we are today.
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The original Color Graphics Adapter (CGA) traces its ancestry
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directly from commercial television. Commercial TV refreshes its
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screen exactly 60 times per second with a horizontal scanning
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frequency of 15,750 cycles per second. The IBM CGA display
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utilizes this timing to support the images it generates. The
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total number of horizontal scanning lines traced onto the screen
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by a CGA system can be determined simply by calculating how many
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horizontal lines are scanned out during one vertical scan. Since
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the screen is scanned vertically 60 times per second, we divide
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15,750 by 60 to yield the horizontal line count of 262. Two
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hundred of these scan lines are used to display actual image
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data, with the balance used to illuminate the CGA screen's border
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region.
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As we all remember, the CGA was not known for producing highly
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legible text (for some it's not yet a memory). The prime
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determiner of text quality is the number of individual pixel
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dots which are available to display individual characters.
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Dividing 200 total image lines by 25 lines of text yields just 8
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scanning lines available per text line. Then since the CGA
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adapter was able to display 640 dots across a horizontal line,
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dividing this by 80 characters per line yields 8 pixel dots
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horizontally per character.
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So CGA technology yielded a budget of 8 by 8 pixels per
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character. Since it is necessary to separate characters by at
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least one blank pixel, and since characters are taller than they
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are wide, CGA characters were designed to fit within a rectangle
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of dots 5 wide by 7 dots high. If you have a few moments to
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spare some time with some graph paper, try designing an entire
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upper and lower case alphabet where each character fits within a
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5 by 7 pixel cell. It's not simple, and there is no really great
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solution.
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Driven by the concern that serious business computer users would
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be very unhappy with the appearance of CGA text, IBM decided to
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provide a better text display alternative. The Monochrome
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Display Adapter (MDA) was the result. In order to deliver more
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legible characters, more pixels are required both horizontally
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and vertically. Where the CGA fits 5 by 7 characters into 8 by 8
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"cells," the IBM monochrome display provides much higher
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resolution: 7 by 9 characters within a 9 by 14 space.
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Changing the character resolution from 5 by 7 to 7 by 9 results
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in a tremendous improvement in character legibility, and a 2-
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pixel horizontal inter-character spacing with a 5-pixel vertical
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spacing leaves the display's characters feeling quite uncrowded.
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The question is, where did IBM get all those extra scan-lines?
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25 lines of text with 14 scan-lines per line means a total of
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350 active scan lines compared to the CGA's 200! The scan-line
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count can be increased by increasing the horizontal scan
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frequency so that more lines are scanned per second, or by
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decreasing the overall vertical refresh rate thus allowing more
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time to scan the horizontal lines.
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IBM did both of these things to create the MDA standard. The MDA
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refreshes its screen at only 50 cycles per second with a
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horizontal scan rate of 18,432 hertz. Now, dividing 18,432 by 50
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yields about 368 scan lines. Since 350 of these are required for
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text display, the MDA is not able to display a border.
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But how can IBM refresh the MDA screen at only 50 cycles per
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second if we begin noticing a flicker as refresh frequencies
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fall below 60 cycles per second? IBM compensated for our lack of
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vision persistence by designing a highly persistent green
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phosphor into their monochrome display. Many people immediately
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noticed a "smeary" effect whenever the IBM monochrome display
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scrolled text. This smearing was created by the use of a long
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persistence phosphor which continued to glow long after the
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screen's electron beam stopped refreshing the region.
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If you've ever noticed an annoying continuous flicker from an
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inexpensive clone monochrome display, now you know why. Most
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clone monochrome displays use less expensive standard short or
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medium-length phosphors... which are inadequate for masking the
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very noticeable effects of the MDA's lower refresh rate. Also,
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since the flicker-perception phenomenon is extremely subjective,
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many people perceive flicker where others don't. I've
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learned that I don't see flicker where other people are being
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driven nuts by it.
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With an understanding of the interactions of horizontal and
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vertical scan rates and display resolution we're ready to
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explore the EGA, VGA and multisync technologies.
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The role of Hercules Graphics,
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and the evolution of the EGA
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We've seen how IBM designed their MDA monochrome display system
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to deliver extremely well-formed characters by increasing the
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display's horizontal scanning rate and decreasing the vertical
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refresh rate. Before continuing our discussion of EGA, VGA, and
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multisynchronous monitors, it's important to understand another
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quite well established and significant display standard,
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Hercules.
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Perhaps IBM simply overlooked the idea of monochrome graphics
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altogether, or underestimated the demand for the display of
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graphic information. More likely though, IBM felt that the word-
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processing market toward which they were targeting their
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monochrome display system had no need to display graphics. How
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could IBM, or anyone for that matter, have anticipated the
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phenomenal effect Lotus' 123 spreadsheet product would have upon
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the IBM compatible market?
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While columns of numbers are indeed informative, the ability to
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graphically display, correlate, and view the results of
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spreadsheet calculations is extremely useful. The folks at
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Hercules Computer quickly recognized this and designed a
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wonderful solution which, with the early support of Lotus, became
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a solid standard.
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Since the Hercules high resolution mode was designed to operate
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with an IBM or compatible monochrome monitor, at a horizontal
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sweep rate of 18,432 cycles per second and a refresh frequency
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of (only) 50 hertz, it could directly leverage the extremely
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high resolution which IBM had designed into their monochrome
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text system. The Hercules monochrome display resolution of 720
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by 350 pixels made the CGA's 640 by 200 look quite sad when
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compared side by side, and suddenly people could have both
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readable text and great looking graphics at the same time and
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from a single system.
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IBM's next move demonstrated that they'd been listening to their
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user's complaints about the low resolution of the CGA standard.
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They were also watching the guys at Hercules make money like
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crazy and were attempting to serve the always mixed blessing
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requirements of full backwards compatibility. The IBM Enhanced
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Graphics Display was IBM's second generation solution, and
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it rapidly became a new standard for the industry.
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By recognizing the CGA system's crying need for better text, IBM
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saw that it had to crank up the scan line count to something
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more like their monochrome display; however, since full-color
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long persistence phosphor monitors are barely affordable by
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small countries, IBM knew that it couldn't play the trick of
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getting the scan line count up by lowering the system's overall
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refresh rate below 60 cycles per second. The only alternative was
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to push the system's horizontal scanning frequency higher than
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the monochrome system's.
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This would mean that their new EGA display system would not be
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backwards compatible to the existing installed base of 200 scan
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line resolution CGA software. (The non-optimal solution crimes
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which are continually committed in the name of backwards
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compatibility is probably my single
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biggest pet peeve. It directly accounts for the unprogrammablity
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of the Intel microprocessor instruction set!) So, in order to
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achieve CGA compatibility from their new EGA system, IBM
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invented the "bi-synchronous" display system.
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By inverting the polarity of the EGA monitor's Vertical
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Synchronization signal, the EGA adapter is actually able to
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switch the EGA monitor between two separate modes: The CGA's
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horizontal sweep rate of 15,750 cycles per second and the newly
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invented EGA horizontal rate of 21,800 cycles per second. The
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15,750 hertz rate yields a CGA software compatible resolution of
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200 lines, while the 21,800 hertz rate results in a full
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Hercules-type resolution of 350 lines. In EGA graphics mode, this
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results in a significant, Hercules-similar resolution of 640
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by 350 pixels.
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Since IBM seems determined not to kick the horizontal resolution
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of these systems up above 640 pixels, we don't quite get the full
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character separation beauty of MDA and Hercules text. On the
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other hand, the EGA's character resolution budget
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of 8 by 14 pixels is significantly better than the CGA budget of
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8 by 8 and allows lower case characters with descending tails
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like "g," "p," "q," and "y" to be imaged cleanly. The EGA's
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resulting well-formed characters made most people happy.
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The EGA's final addition to the CGA standard was the provision
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for additional colors. Where the CGA display could display 8
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colors in either of two intensities, bright or dim, the EGA
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display, when operating in EGA mode, allowed each of its three
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primary colors, Red, Green, and Blue, to be mixed together in
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any of four intensities. Therefore 4 times 4 times 4, or 64
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total colors could be displayed by IBM's EGA display. Though
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technology has passed the EGA monitor by, it represented an
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adequate, backward compatible, unification of the CGA, MDA, and
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Hercules standards.
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IBM's recognition of the EGA's shortcomings
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with the creation of the VGA "standard"
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On our journey toward the goal of selecting the best possible
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display system for the least possible money for Steve's Dream
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Machine, we've traced the evolution of IBM compatible display
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system technology from the original CGA and MDA standards
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through the development of the Hercules and EGA standards. IBM's
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announcement of its new generation PS/2 machines offers yet
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another display system to "the standard" throne. Oddly named
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after the integrated circuit chip which implements it, the Video
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Graphics Array, or VGA, has provided enough new cleverness and
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innovation to displace the prior EGA standard.
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With graphic user interfaces gaining ever more market
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recognition and IBM's own OS/2 Presentation Manager on the
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horizon, IBM needed to push their graphics resolution offering
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above the EGA's 640 by 350. At the same time, IBM wished to
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further enhance the system's color capabilities, probably to
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further differentiate itself from Apple Computer's
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monochrome Macintosh products and to better compete with Apple's
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newer colorful Mac II. To further confuse things, this was all
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happening at a time when IBM was determined to lower its
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manufacturing costs.
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While the EGA display was innovative with its split-personality
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dual-frequency horizontal sweep rate in order to deliver both
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350 line vertical resolution without sacrificing 200 line CGA
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compatibility, is was more expensive to manufacture than IBM was
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now happy with. IBM made a brilliant move in their VGA system
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which completely eliminated the need
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for the expensive frequency changing display while actually
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enhancing the appearance of older CGA-style text and graphics.
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The VGA's fixed horizontal sweep rate of 31,500 cycles per
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second offers several wonderfully clever savings. In the first
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place, dividing the horizontal rate of 31,500 hertz by the 60
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cycle vertical rate yields 525 total horizontal lines scannable
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during one screen. This high scan line count delivers even
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better legibility from VGA text which now has a text character
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pixel budget of 8 by 16, while the EGA's barely adequate high
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resolution line count of 350 jumps up to a very respectable 480.
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The excess line count (the difference between the 525 total and
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the 480 used) even allows a tidy 1/4 inch border in all modes.
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The VGA's cleverness stems from two additional things which IBM
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did in order to deliver backward compatibility to the CGA and
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VGA. The VGA monitor's very fast horizontal scan rate put IBM in
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the enviable position of actually having, in some cases, too
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many scan lines, rather than too few. So in such cases IBM
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slightly INCREASES the vertical refresh rate (to above 60 hertz)
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in order to trim back on the number of lines displayed when they
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need fewer.
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Secondly, rather than slowing the display's HORIZONTAL rate
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drastically down to the CGA's 15,750 cycles, in order to deliver
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just 200 horizontal scan lines, the VGA raises its VERTICAL rate
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just slightly up to 70 hertz which yields 400 scan lines. Then a
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clever double-scanning approach is used to emulate the CGA's 200
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line mode. Double scanning simply repeats each of the CGA's
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lines twice and results in a higher resolution appearance while
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maintaining complete software backward compatibility.
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The only remaining "tweak" required involves keeping the VGA's
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displayed screen height constant which the IBM VGA monitor
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achieves by sensing the polarity of the Vertical Synchronization
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signal sent to it by the VGA adapter. The monitor uses the
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Vertical Sync signal polarity to adjust the spacing between
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successive scan lines so that the VGA's image is kept almost
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uniformly sized throughout the increasing jungle of new, old,
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and older display modes.
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Thus the VGA system scans 350, 400, and 480 lines to achieve
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CGA, EGA, and VGA compatible display modes while leaving the
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horizontal scanning rate set to a constant 31,500 hertz and only
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tweaking the vertical refresh rate between a happy 60 and 70
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cycles per second. The result is a simpler and far less
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expensive VGA monitor which exceeds the EGA's capabilities and
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delivers far cleaner CGA emulation.
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The other major change presented by the VGA system is an
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expansion of the system's color capabilities. The original CGA
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monitor utilized one signal each for Red, Blue, and Green
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colors, and an additional single signal for intensity which
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delivered 16 total possible colors. The EGA expanded upon this
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by providing two signals each for the Red, Green, and Blue
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colors, thus delivering four intensities of each color, with 64
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color mixtures possible. The VGA's color system operates in an
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ANALOG rather than DIGITAL fashion where varying voltages, rather
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than ON/OFF signals are provided for each color for mixing.
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Software and memory limitations pare the resulting infinite
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color possibilities down to a maximum of 256 colors chosen from
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a total palette of 262,144 in some display modes.
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NEC's Brilliant Creation of the Multisync,
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and 800 by 600 Resolution Graphics
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We've taken a detailed look at the evolution of IBM compatible
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display systems, focussing almost exclusively upon the multitude
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of standards which have first been set then soon superseded by
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IBM. We've seen that the various display adapters have always
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been "tightly coupled" to their display monitors and have
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frequently employed fancy "kludge" solutions (like conditional
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inverting of synchronization signal polarities) when necessary
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to maintain backward compatibility to the multitude of prior
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standards.
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Amid the wilderness created by the incredible array of vertical
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and horizontal scan rates, a solid alternative to the eternal IBM
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lock-step frenzy has arisen. Originally conceived by Nippon
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Electric Corporation (NEC) as an answer to just this problem, the
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so-called "multi-synchronous" display monitors are now selling in
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the hundreds of thousands for a very good reason.
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In what could only be called a truly astounding leap of insight,
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the designers at NEC integrated the past and predicted the
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future when they invented their original NEC Multisync, a single
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unified display monitor solution for all adapter technologies
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past, present, and future. Rather than following IBM with yet
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another tightly coupled clone display monitor, NEC invented a
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single monitor which quietly displayed anything it might be
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handed by the system's display adapter. By accepting an unheard
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of range of vertical and horizontal synchronization frequencies,
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as well as both digital and analog RGB intensity signals, the
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NEC Multisync became virtually obsolescence-proof.
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While IBM was busily requiring all of its EGA owners to
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completely scrap their "yesterday's solution," EGA monitors which
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would no longer be compatible with the VGA of today (and
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tomorrow?), and purchase the all new VGA displays, proud
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Multisync owners only needed to change their monitor's cable
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then flip a couple of switches at the rear of their displays.
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That's what I call truly brilliant engineering!
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Of course it wasn't long until everyone else recognized NEC's
|
|
brilliance and began cloning multisynchronous monitors like mad.
|
|
Today's mail order ads are drenched in "generic multisynch-ness"
|
|
because it's simply the right way to go.
|
|
|
|
However, there's something else which makes multisynching the
|
|
right solution, and after extensive experimentation and
|
|
comparison it has become an INFINITELY CRITICAL COMPONENT of
|
|
Steve's Dream Machine: Support of the wonderful 800 x 600 pixel
|
|
super high resolution modes which are now available from all
|
|
state-of-the-art EGA and VGA display adapters.
|
|
|
|
Many of you will remember that Steve's Dream Machine and I have
|
|
been holding onto monochrome display technology for dear life...
|
|
looking to monitors such as the Wyse-700/Amdek-1280 and MDS
|
|
Genius to provide the truly useful bit-mapped graphics
|
|
resolution which is, and will be, required by today's and
|
|
tomorrow's desktop publishing, MS Windows, and OS/2 Presentation
|
|
Manager applications. Until many months of searching yielded the
|
|
incredible, ultimate, adapter/monitor combination, I didn't
|
|
believe that a color system could really deliver "truly useful"
|
|
(and in fact wonderful) high resolution bit-mapped displays. It
|
|
can. I'll tell you about the results of my quest, but first we
|
|
need a bit more foundation...
|
|
|
|
It turns out that truly useful bit-mapped resolution requires
|
|
stepping above even the VGA's new 640 by 480 resolution up to
|
|
800 by 600. By cranking the horizontal sync up to 35,100 and
|
|
sneaking the vertical refresh just a tad below 60 hertz to about
|
|
56, any solid multisynchronous monitor can readily display 600
|
|
lines of 800 full color pixels per line.
|
|
|
|
There's something magical about the difference between 640 by
|
|
350, 640 by 480, and 800 by 600. It's a staggering difference.
|
|
The prior two resolutions simply pale by comparison to 800 by
|
|
600. Trying to understand why things get so incredibly better as
|
|
the resolutions are increased, I've decided that it's because
|
|
the total pixel count increases with the PRODUCT of the
|
|
horizontal and vertical resolutions. This is a powerful
|
|
relationship. For example, on a screen with square resolution,
|
|
the total pixel count would increase with the SQUARE of the
|
|
screen's edge resolution, so a DOUBLING of edge resolution
|
|
produces a QUADRUPLING of the total pixel count. Consequently
|
|
the standard EGA resolution of 640 by 350 contains only 46% of
|
|
the pixel count of 800 by 600, and even the VGA offers only 64%.
|
|
800 by 600 resolution delivers 156% of the VGA's pixel count.
|
|
|
|
So at this juncture we must leave IBM in the dust. Only enhanced
|
|
EGA and VGA adapters are able to generate 800 by 600 pixels, and
|
|
only multisynchronous displays can lock onto the extreme
|
|
synchronization frequencies required for the delivery of this
|
|
stunning and readily available resolution.
|
|
|
|
|
|
The Incredible SONY CDP-1302A...
|
|
Steve's Dream Machine Monitor of Choice!
|
|
|
|
|
|
|
|
Having decided that Steve's Dream Machine monitor had to be
|
|
multisynchronous in order to deliver the most resolution
|
|
possible, the next obvious question was: Which one was the best?
|
|
After staring endlessly at, and touching and feeling, just about
|
|
every available candidate, I determined that no other monitor
|
|
comes anywhere NEAR the quality of the Sony "Multiscan" CDP-
|
|
1302A. The Sony Multiscan is solidly entrenched as the Steve's
|
|
Dream Machine video display monitor. After purchasing several, I
|
|
couldn't be more pleased.
|
|
|
|
The single feature which distinguishes the CDP-1302A from the
|
|
crowd, placing it heads and shoulders above the rest, is its
|
|
image quality. Based upon Sony's legendary Trinitron color
|
|
picture tube, the 1302A packs its primary red, blue, and green
|
|
phosphors so closely together that white text actually looks
|
|
white, rather than appearing as an ugly island of white fringed
|
|
with red on one side, green on top, and blue on the other side.
|
|
|
|
Coming from the purely monochrome character coloring of
|
|
monochrome displays as I did, I just wasn't willing to sacrifice
|
|
text color purity for the sake of color. The Sony 1302A is the
|
|
ONLY monitor in the industry which doesn't compromise text
|
|
appearance for color capability. As I write this column with PC-
|
|
Write, I'm staring at white text on a blue background. With my
|
|
nose one inch from the screen, aside from being cross-eyed, I
|
|
absolutely cannot see anything but white text on a blue
|
|
background. No other monitor delivers this quality.
|
|
|
|
All contemporary color monitors operate through a process known
|
|
as "SPATIAL COLOR MIXING." Though from a distance the screen
|
|
appears smooth, homogeneous and continuous, it's actually
|
|
composed of thousands of individual red, green, and blue
|
|
phosphor regions. When the display's electron beams strike the
|
|
phosphors from behind they fluoresce and glow in one of the three
|
|
primary colors. By controlling the instantaneous voltages applied
|
|
to each of the three electron beams at the back of the CRT, the
|
|
red, green, and blue color phosphors in the region
|
|
where the beams are striking are made to glow in proportionate
|
|
brightness.
|
|
|
|
Our eyes, having somewhat limited resolution, don't see the
|
|
individual red, green, and blue phosphors in the region, but
|
|
instead spatially mix these colors into a single composite.
|
|
|
|
(It's rather incredible to realize then that the first thing our
|
|
eyes do is to re-separate this composite color back into its
|
|
red, green, and blue color levels since our eyes are built from
|
|
light sensitive rods and cones which selectively respond only to
|
|
red, green, and blue light!)
|
|
|
|
However, our eye's ability to convincingly spatially mix the
|
|
screen's primary colors is a function of the center-to-center
|
|
inter-color spacing, which is also known as the display's "DOT
|
|
PITCH." Not only does the Sony have a significantly tighter dot
|
|
pitch than any other large display in the industry (0.26
|
|
millimeters versus 0.31 or coarser for everyone else), but the
|
|
Sony's Trinitron'ness seems inherently better suited to the job
|
|
of helping our eyes to perform this mixing. It's almost as if
|
|
the individual colors are being pre-mixed behind the screen
|
|
before leaking out onto the tube's glass faceplate.
|
|
|
|
This dot pitch also means quite a lot when the monitor is being
|
|
called upon to display higher resolution images. As the number
|
|
of displayed pixels per inch begins to approach the number of
|
|
phosphor dots per inch a strange interaction known as "SPATIAL
|
|
FREQUENCY BEATING" occurs. You can most easily see this by
|
|
drawing single pixel wide horizontal, vertical, or slanted black
|
|
lines against a solid white background. Rather than appearing as
|
|
black, the line's width is so much smaller than the surrounding
|
|
illuminated pixels that these too-fat pixels bleed their colors
|
|
into the supposedly black line, rendering a non-black dimly
|
|
colored line. In practice, high resolution black on white
|
|
applications such as desktop publishing end up appearing
|
|
disturbingly multi-colored rather than pleasingly black on
|
|
white. The 800 by 600 pixel resolution which multisync displays
|
|
provide at no cost requires the dot pitch to be as tight as
|
|
possible.
|
|
|
|
If you care about your eyes, I urge you to check into the Sony
|
|
Multiscan CDP-1302A. This is NOT a place to compromise.
|
|
|
|
|
|
|
|
And the Paradise VGA Plus Card,
|
|
The Ultimate VALUE in VGA Adapters
|
|
|
|
|
|
Having answered the burning question of the ultimate video
|
|
monitor for Steve's Dream Machine with my enthusiastic ravings
|
|
about the marvelous Sony CDP-1302A multiscan monitor, the final
|
|
question to be answered for our display sub-system project is:
|
|
What's the ultimate display adapter?
|
|
|
|
Determining the correct answer to this question was complicated
|
|
substantially by the simple fact that the VGA marketplace is
|
|
filled with an incredible degree of clutter, misdirection,
|
|
overstatement, and outright lies. What you see and hear is
|
|
almost always FAR FAR different from what you actually get. Wild
|
|
claims made by VGA adapter manufacturers abound, the ads are
|
|
largely full of baloney, and it's quite hard to really know
|
|
what's true. It's also quite hard to know what really makes a
|
|
DIFFERENCE in VGA adapters, so consequently even the normally
|
|
shrewd buyer will wind up guessing.
|
|
|
|
As my research into VGA adapters progressed, and I learned more
|
|
and more, I became increasingly upset by the state of affairs and
|
|
committed a disproportionate amount of time and energy to
|
|
the task of finding out what's REALLY going on. Getting
|
|
underneath the covers to substantiate or debunk various claims
|
|
required the creation of special benchmarking software to
|
|
directly measure critical adapter parameters such as horizontal
|
|
sweep rates, overall vertical refresh rates, and raw low-level
|
|
adapter data bandwidths. What I discovered amazed me, and even
|
|
though the results of this research may upset some significant
|
|
players in the industry, I feel compelled to share what I found.
|
|
|
|
Since I don't want to tease you any more than necessary, I'm
|
|
telling you right up front, here and now, that for my money,
|
|
there is no adapter in the industry which delivers more overall
|
|
value than the inexpensive, analog-only, 8-bit, incredible
|
|
Paradise VGA Plus. Though the VGA Plus is currently in very
|
|
short supply, being affected both by its own popularity as well
|
|
as by our industry's current dynamic RAM shortage, it's an
|
|
incredible value at its current street price of between $230 and
|
|
$260.
|
|
|
|
I urge you not to purchase any other display adapter, VGA or
|
|
otherwise, until you've heard me out. Though you might have to
|
|
struggle and/or wait a while to find one, it'll be a decision
|
|
you couldn't regret.
|
|
|
|
The various VGA adapters in the industry may be differentiated
|
|
by applying the following tests and comparisons: raw low-level
|
|
data bandwidth, companion software drivers, display monitor
|
|
compatibility, IBM VGA register level compatibility, system-
|
|
level hardware compatibility, and to a lesser degree backward
|
|
compatibility with prior display standards.
|
|
|
|
Of all these characteristics, only video display compatibility
|
|
and backward compatibility are obvious from the surface. Every
|
|
other characteristic must be determined through actual use and
|
|
testing. The only negative feature of the Paradise VGA Plus in
|
|
this regard is it's total lack of support for the older digital-
|
|
only monitors including the original IBM monochrome, CGA, and
|
|
EGA displays. You won't be able to use the VGA Plus if you have
|
|
one of these, though Paradise has stated that they will make a
|
|
version of their card for sale to large OEM customers which will
|
|
support both digital and analog monitors. This liability is
|
|
shared by the Compaq and Video Seven Fastwrite and VRAM cards,
|
|
so the Paradise is in good company. Of course this is no problem
|
|
if you already own or intend to purchase any multisync monitor
|
|
like Steve's dream monitor, the Sony CDP-1302A.
|
|
|
|
Almost every VGA adapter in the industry is a so-called "five-
|
|
in-one" card. Five-in-one refers to MDA, CGA, Hercules, EGA, and
|
|
VGA, and means that such cards can run virtually any software
|
|
ever written to any of these major standards. The two notable
|
|
exceptions are IBM and Compaq which lack support for the
|
|
Hercules standard. Even though Compaq's VGA adapter utilizes the
|
|
Paradise PVGA1A VGA chip, and could thus have easily implemented
|
|
Hercules backwards compatibility and the useful extended
|
|
resolutions as do the Paradise VGAs, Compaq chose not to bring
|
|
these features to their purchasers, apparently preferring to
|
|
remain more strictly IBM compatible. For this reason, and
|
|
considering its high price, you'd have to really love the Compaq
|
|
name in order to intelligently purchase Compaq's VGA adapter.
|
|
It's a very nice adapter, but the Paradise Plus or Pro do more,
|
|
cost less, and are otherwise identical, all being based upon the
|
|
same VGA chip.
|
|
|
|
|
|
|
|
Display System Performance
|
|
|
|
|
|
It's hardly surprising that the single hottest issue in the VGA
|
|
marketplace is performance. People want machines that don't
|
|
slow them down, and since our video display screens are the
|
|
windows into the souls of our machines, it's only natural to
|
|
want a screen that can keep up with the CPU which lurks behind.
|
|
|
|
Being a performance fanatic myself, the first thing I did was to
|
|
write a machine language benchmarking program to determine the
|
|
fundamental raw machine-level data throughput of VGA adapters.
|
|
As a low-end reference point, the true Blue IBM VGA adapter can
|
|
accept text data at 569 Kbytes per second and graphics data, when
|
|
in 640 by 480 resolution, at 592 Kbytes per second.
|
|
|
|
The IBM's raw text throughput of 569 Kbytes per second means
|
|
that the entire 4000 byte text screen could be re-written 142
|
|
times per second. Since display screens are only displayed 60 to
|
|
70 times per second, anything faster than this is completely
|
|
invisible and represents wasted performance. The point is, when
|
|
displaying a 25 line by 80 column text screen, even the SLOWEST
|
|
VGA card on the market (which the IBM VGA is) is twice faster
|
|
than is even visible! Those "8 times faster" performance claims
|
|
being made by several VGA competitors are based upon their
|
|
card's text-mode throughput and are about as useful as a jet
|
|
engine on a skateboard. I ignore such nonsense and the companies
|
|
behind it.
|
|
|
|
However, what's true for text mode performance is not
|
|
necessarily true for bit-mapped graphics. While an entire text
|
|
screen is specified by just 4000 bytes of data, a 16-color 800 by
|
|
600 high resolution bit-mapped image requires 240,000 bytes of
|
|
data! Even so, IBM's 592 Kbytes of graphics throughput can still
|
|
paint an entire VGA image in four-tenths of one second. That
|
|
really isn't bad.
|
|
|
|
So how do the other boards in the market compare? Well any board
|
|
based upon the Tseng Labs (pronounced sang) chipset will deliver
|
|
approximately IBM-grade performance. Tseng Labs based boards
|
|
such as those from Genoa, Orchid, Sigma, STB, and Tecmar have
|
|
throughputs of 591 Kbytes for text and 588 Kbytes for graphics,
|
|
which is actually a bit slower than IBM. The advantage these
|
|
boards have over the IBM is 5-in-1 backwards compatibility.
|
|
Unfortunately, this comes with an expense of yawning performance.
|
|
Several also utilize the Tseng Labs 1024 by 768 resolution mode.
|
|
This requires display screen interlacing which halves the overall
|
|
refresh rate and produces completely unacceptable display flicker
|
|
when using Ventura or with Window's color mixing scheme known as
|
|
dithering. One positive feature of these cards is their full
|
|
support for the digital-only MDA, CGA, and EGA monitors, but
|
|
since such monitors aren't state-of-the-art anyway, it would be a
|
|
shame to choose a poor performing VGA adapter for the sake of
|
|
running a poor performing display. For these reasons, I don't
|
|
recommend Tseng Labs chip based VGA adapters.
|
|
|
|
Video Seven has been generating quite a lot of press attention
|
|
lately with their FastWrite and VRAM VGA adapters. Having
|
|
studied these boards at length with the hope that they would
|
|
turn out to be real screamers, I have to admit to being less
|
|
than fully impressed. I had significant hardware and software
|
|
incompatibility problems with the FastWrite and VRAM boards and
|
|
none with any others. Though I've heard that newer revisions
|
|
have solved many of the earlier problems, I still feel shy toward
|
|
them. Also, the incompatible way their video BIOS was designed
|
|
prevents multitasking software from freely and properly
|
|
switching tasks between various extended modes. This alone would
|
|
keep me away from Video Seven's products.
|
|
|
|
However, it can't be denied that the Video Seven pair are
|
|
uncontested winners when raw throughput alone is considered. In
|
|
640 x 480 mode, the FastWrite came in with 1.812 megabytes per
|
|
second throughput, and the VRAM delivered a screaming 2.885
|
|
megabytes per second.
|
|
|
|
I was puzzled at this point because my favorite little Paradise
|
|
Plus board, with its 1.139 megabytes per second throughput, just
|
|
didn't SEEM to be any slower than the VRAM. It occurred to me
|
|
that the board's raw throughput was being "watered down" by
|
|
"software overhead" which would tend to equalize performance.
|
|
After writing a new set of benchmarks to test performance
|
|
THROUGH their respective Windows drivers, I found what I
|
|
expected. Despite the fact that the VRAM board could accept raw
|
|
bit-map data 153% faster than the Paradise Plus, the software
|
|
overhead in the Windows drivers resulted in a performance
|
|
difference of only 54%! When the application's own overhead was
|
|
factored into this, the VRAM edge was even further blunted.
|
|
|
|
Due to architectural characteristics of the Paradise PVGA1A VGA
|
|
chip, Paradise's 16-bit boards actually deliver NO MORE
|
|
PERFORMANCE than the inexpensive 8-bit Paradise Plus, Steve's
|
|
Dream Machine VGA board.
|
|
|
|
|
|
|
|
The Display System Series
|
|
Loose Ends
|
|
|
|
|
|
|
|
Let's finish our study of the state of the art in IBM video
|
|
display technology by tying down a variety of loose ends. As
|
|
we've seen, my display adapter of choice is Paradise's 8-bit VGA
|
|
Plus. Surprisingly, the architecture of the PVGA1A chip, which
|
|
forms the heart of every VGA adapter from Paradise as well as
|
|
the VGA systems produced by AST Research and Compaq, gains
|
|
NOTHING from a 16-bit bus connector when the boards are used in
|
|
their high resolution bit-mapped modes. This means that except
|
|
for the additional memory on the Paradise VGA Pro board, there's
|
|
absolutely no benefit to purchasing it over the less expensive
|
|
8-bit Paradise Plus. In fact, the temptation would then be to
|
|
run the Pro card in its 256 color mode, but my benchmarks
|
|
revealed that display performance suffers with higher color
|
|
counts. This is hardly surprising since additional colors depend
|
|
upon the use of additional memory which must be managed by the
|
|
driving software.
|
|
|
|
After declaring the Sony "Multiscan" CDP-1302A to be today's
|
|
ultimate video display, I was contacted by many competing vendors
|
|
who wanted me to believe that their displays were better. As a
|
|
result of entertaining several such possibilities I'm more
|
|
certain now than ever that the Sony blows EVERYTHING else away.
|
|
|
|
As I acquire increasing experience with 800 by 600 resolution,
|
|
which you get "free" when the Sony is paired with the Paradise
|
|
VGA Plus, I'm becoming more and more certain that it's ultimately
|
|
the best general purpose resolution. When running at 800 by 600
|
|
resolution, the Sony produces an active image area which is 10
|
|
inches wide by 7.5 inches tall. Dividing each of these lengths
|
|
into the pixel resolution in that dimension yields exactly 80
|
|
pixels per inch IN EACH DIRECTION. This beats the Macintosh's 72
|
|
ppi resolution with a much larger screen while delivering the
|
|
Macintosh's popular "square" pixels which are exactly as wide as
|
|
they are tall. It's nice to have a system on which circles
|
|
appear circular and squares really are square!
|
|
|
|
While I'm thinking about high resolution under Microsoft
|
|
Windows, I really need to make sure you know about Micrografx's
|
|
incredible Designer product. Designer feels to me like a highly
|
|
evolved CAD package with an exquisite state-of-the-art Windows
|
|
user interface. Using Designer has become fast and reflexive. It
|
|
has that rare easy-to-learn feeling which results from several
|
|
generations of detail polishing. While Designer completely
|
|
answers my desire for the lightning fast creation of structured
|
|
graphics, I've been surprised and delighted to find that several
|
|
of my died-in-the-wool traditional "CAD freak" friends have
|
|
completely switched to Designer after seeing me mouse my way
|
|
around it. If you have any need for PC based drawing, I'd urge
|
|
you to take a peek at Micrografx's Designer.
|
|
|
|
I'm addicted to Ventura Publisher for the creation of all manner
|
|
of high grade hard copy, so the quality and legibility of
|
|
Ventura's displayed image has profound importance for me. If
|
|
you've been reading this column for long, you probably know that
|
|
I tend toward perfectionism, always needing to get the most out
|
|
of my system. So I've been irked by Ventura's three fixed
|
|
display screen zoom factors. At each zoom setting the image is
|
|
always either too small, leaving an unused "grey zone" to the
|
|
right of the page's image, or too large, requiring a horizontal
|
|
scroll to see everything.
|
|
|
|
Bitstream Inc. has developed and sells a fabulous technology
|
|
called FONTWARE which generates any size and resolution of
|
|
ultra-high-quality typefaces from a set of sophisticated
|
|
typeface outline masters. Since the EGA's pixels aren't square,
|
|
the EGA-compatible screen fonts which are shipped with Ventura
|
|
aren't specifically tailored for 800 by 600 resolution. So I
|
|
decided to used Bitstream's Fontware to regenerate an entirely
|
|
new set of Ventura screen fonts with SQUARE pixels, and while I
|
|
was at it, to choose a screen font resolution which would give
|
|
me EXACTLY the Ventura zoomed sizes I wanted.
|
|
|
|
After some experimentation, I'm delighted to tell you that I now
|
|
have exactly what I want from Ventura. By asking Bitstream's
|
|
Fontware technology to rebuild Ventura's screen fonts at 100 by
|
|
100 pixel resolution the text of a standard 8.5 by 11 inch page
|
|
with one inch margins EXACTLY FILLS the screen in Ventura's
|
|
"normal" viewing mode with Ventura's mode selection icons
|
|
displayed. The result is an incredibly clear and legible image
|
|
in 800 by 600 resolution which puts the VGA's defacto 640 by 480
|
|
image to shame.
|
|
|
|
Micrografx can be contacted about Designer at (800) 272-3729 and
|
|
Bitstream can tell you more about Fontware at (800) 522-3668.
|
|
|
|
- The End -
|
|
|
|
Copyright (c) 1989 by Steven M. Gibson
|
|
Laguna Hills, CA 92653
|
|
**ALL RIGHTS RESERVED **
|
|
|
|
|
|
|
|
Another file downloaded from: NIRVANAnet(tm)
|
|
|
|
& the Temple of the Screaming Electron 415-935-5845
|
|
Just Say Yes 415-922-1613
|
|
Rat Head 415-524-3649
|
|
Cheez Whiz 408-363-9766
|
|
Reality Check 415-474-2602
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|
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|
Specializing in conversations, obscure information, high explosives,
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|
arcane knowledge, political extremism, diversive sexuality,
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|
insane speculation, and wild rumours. ALL-TEXT BBS SYSTEMS.
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