333 lines
16 KiB
Plaintext
333 lines
16 KiB
Plaintext
THE INTEL MICROPROCESSOR
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This article contains a few, very mildly edited pages from the Exam Cram Server+ book by
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Deborah Haralson and Jeff Haralson (ISBN 1-58880-106-3). This document was typed up
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by Jonathan Smith.
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If you are interested in learning more, I suggest you buy the book
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And now, on with the article...
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BOOK: Exam Cram Server+
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AUTHORS: Deborah Haralson
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Jeff Haralson
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ISBN: 1-58880-106-3
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PAGES: 71 - 78
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DATE: 4:30 PM 8/20/2002
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Intel 8080
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----------
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The 8080 was first commercfially produced in 1974. It was the processor in the Altair 8800
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home computers. The Altair name comes from a Star Trek planet, which let the computer where
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it has never gone before. This computer was placed on the market by the MITS calculator
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company and was sold in kit form. Bill Gates and Paul Allen wrote the BASIC programming
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language for MITS, which was used on the Altair computer, and it started Bill's meteoric
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rise to his present level of success.
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Intel 8086 and 8088
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-------------------
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The Intel 8086 was released on June 6, 1978. It was Intel's first 16-bit microprocessor.
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It was designed to be fast and powerful. The 8086 boasted a 4.77 to 10 MHz clock speed, 16-
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bit registers, and an external 16-bit data bus. It also had a 20-bit address bus to address
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1MB of RAM. When IBM entered the computer business, the 8086 was considered too expensive,
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and oddly enough, too powerful to fulfill "Big Blue's" vision of a computer. The result was
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that Intel essentially "dumbed down" the 8086 processor and called it the 8088.
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At this point, some of the factors that affected the overall speed of a computer can really
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be identified. The 8086 and the 8088 could run the exact same program and could be set to
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the exact same clock speed. The 16-bit data bus would let the 8086 import and export the
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data to the chip at twice the speed of the 8088.
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Intel 80286
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The Intel 80286, commonly called the 286, started as a 6 MHz speed demon. Soon Intel pushed
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the envelope by upping the clock speed to 10, 12.5, and eventually 20 MHz. To add to the
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power, the 286 came with a 24-bit address path that allowed for a whopping 16MB of
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addressable memory. This chip was the heart of the IBM AT computer.
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The 286 also offered two modes of operations: real mode and protected mode. These two
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modes of operation made the package operate like two separate chips in one package. Real
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mode operations essentially acted like an 8086 microprocessor. The computer could run the
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8088 and 8086 programs without requiring any modifcation to the programs. Every system
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instruction was available and fully functional when the 286 was operating in real mode.
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This level of compatibility came at a price. The 80286 microprocessor essentially
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lobotomized itself, cutting back the addressable memory to 1MB. This made the old programs,
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not to mention the owner of the aformentioned programs, happy, but limited the full
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flexibility and functionality of the machine.
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Protected mode operations allowed specially programmed applications many advantages over the
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older real mode programs. Protected mode applications were "protected" in that they were
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limited to writing only to their assigned memory. This helped to prevent applications from
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stealing or overwriting areas of memory that was originally designated to a separate
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application. The protected mode helped add stability and reliability to a machine that was
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raplidly becoming indispensable in the business environment.
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The protected mode of operations also heralded in the invention of virtual memory, which
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allowed applications access to far more than the 16MB of physical memory. This meant that
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with up to 1GB of memory, larger applications coul be loaded simultaneously and would be
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protected from fighting each other for memory.
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Bill Gates' MS-DOS had a very tough time addressing this huge amount of available storage, so
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the 286 saw the rise of additional operating systems like Microsoft Windows, SCO Unix, and
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IBM's OS/2. The more powerful, true multitasking operating systems were still in the
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development stage, and the 286 was obsolete by the time some of the "beefier" operating systems
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like Windows 95, Windows NT, and Windows 2000 were introduced.
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One major disadvantage to the two modes in the 80286 microprocessor was that the computer
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needed to be rebooted to change the operational mode. This led to a gradual shift from real
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mode applications to those natively written to take advantage of the many features of the 286.
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Intel 80386
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Intel changed the world of computing when it introduced the 80386 microprocessor in June 16,
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1985. The 80386 was the first true 32-bit processor. All of the support circutry, the
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external bus, the address bus, and the registers were a full 32 bits in width. The chip
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originally shipped with a clock speed of 12 or 16 MHz and could address 4GB of physical RAM
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and 65TB of virtual memory. One of the biggest advantages of the 386 was that it could
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switch between real and protected modes of operation without requiring a reboot.
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The 386 microprocessor introduced an additional operation mode known as virtual real mode.
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This made it possible for the 386 processor to host virtual machines that enabled more than
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one application to actually run at the same time.
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Intel eventually produced 80386 processors that could run at 25 and 33 MHz. Clone
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manufacturers weren't far behind as chief Intel rival, AMD, produced an 80386-compatible
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that ran at an unprecedented 40 MHz.
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Intel charged a pretty menny for the flagship of their processor fleet. The big 80386 was
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out of reach for many businesses, so Intel decided to offer a smaller version that was
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designed to increase sales without dropping the price of the newest kid on the block. In
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June of 1988, Intel released the 386SX.
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386DX and 386SX
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---------------
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The 386DX (Dual word eXternal) was the full-blown 80386 in its entire 32-bit glory. The
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386SX (Single word eXternal) was created by disabling half of the 32 bits of the data bus
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to a single word or two bytes. This drop it to the 16-bit, 286 levels. Intel also dropped
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the memory addressing to a miserly 24-bits, which limited the SX machines to only 16MB of
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RAM.
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The one advantage of the 386SX was that it could be used to upgrade existing 16-bit
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motherboards. This extended the life of users' machines and also temporarily ensured that
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motherboard manufacturers had a few more months to unload their inventory before it all
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became paperweights.
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It was in the 80386-80486 years that Microsoft first produced the Windows operating system,
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and IBM released OS/2. NetWare ruled the server market, and it was only toward the end of
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1990 that Microsoft started beta testing their first NOS, which would be known as Windows NT.
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Meanwhile, Unix was being used in corporate environments since the 8088 became available.
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Intel 80486
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The 486 processor was roughly twice as fast as a 386 running at the same clock speed. The
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four factors that contributed to this fact were:
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- The 486 only took two cycles to execute an instruction, whereas the 386 took 4.5 cycles.
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This meant that the 486 could perform 2.5 operations for every one that the 386 could crank
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out.
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- Intel moved the cache on the chip creating the first Level 1 cache available for mass
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production. This built-in cache had an average hit ration of 90 to 95 percent. This meant
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that when the processor needed data from memory, it was right there most of the time. This
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convenience almost eliminated the need for any wait states on the main CPU.
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- Built-in math coprocessors were included in most versions of the 486. The coprocessor
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that greatly enhanced the mathematical prowess of the older machines was brought onboard
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the main processing chip. This meant no more trips to the bus to request information.
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- Memory could be accessed using burst-mode memory cycles. This meant that the normal
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two-cycle memory access would proposition the circutry for the next data transfer. Once the
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inital 32 bits were transferred in two cycles, the next 12 bytes could be had with only one
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clock cycle for each 32 bits, or 4 bytes. That meant up to 16 bytes of additional data
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could be transferred in as little as five cycles instead of the normal 8+ cycles required
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by the 386.
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The first 80486DX processor was introduced by Intel on April 10, 1998, and the first systems
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started to appear the following year. The inital chip ran at 25 MHz, but remember, this
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outperformed a compatible 80386 50 MHz system.
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486SX
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Intel once again put the brakes on its premier processor to provide consumers with a cheaper,
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but slower, version of its flagship processor. The company accomplished this by removing
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the math coprocessor. Intel initially just turned the coprocessor off. This thrilled many
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hardware hackers as they discovered they could turn it back on and get a more expensive chip
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at a bargain. Intel fought back by actually removing the circuitry. Intel did offer an
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upgrade from the 486SX to the 486DX by installing the OverDrive processor to restore the
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missing circuits, but at the cost of reduced proximity to the main CPU circuitry.
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clock Doubling
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Intel answered the increasing demands of speed by introducing the DX2 and DX4 processors.
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These machines ran at clock speeds of up to 100 MHz by taking the CPU and configuring it to
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run internally at double the external clock speed. This would take a normal 486DX running at
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33 MHz and produce a 66 MHz speed demon. The DX4 would triple the external clock, making the
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same 33 MHz clock runs the chip at 100 MHz. Keep in mind that this only affected the internal
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processes. The internal register transfers and computer would run at 100 MHz, but external
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calls for memory would only run at the normal 33 MHz rate. The DX4 also offered increasing
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amounts of internal onboard cache.
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Pentium Processors
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Because you cannot copyright numbers, Intel decided to move to Latin to name its processors.
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Pentium is derived from the Latin word for five as the Pentium is the new 80586 family of
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microprocessors. The first, or Pentium I, was introduced on October 19, 1992, with the first
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chip shipping on March 22 the following year.
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By this time, many corporations were migrating to client/server solutions that lived outside
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of the mainframe enviromnents with which most people were familiar. Windows NT Server was in
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full swing and competing vigorously with NetWare for an increasing market share. Unix had
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become more popular, however, not as mainstream as the other two network operating systems.
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The Pentium was the first chip to offer superscalar technology. This meant that the Pentium
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featured twin data paths, which allowed the processor to execute two instructions at the same
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time. These two busses were called U and V. The U pipeline was designed to process the entire
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instruction set of the Pentium. The V pipeline offered a subset of instructions. This allowed
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the processor to divide the instructional tasks into discrete operations that were then shared
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between the two pipelines. Software that is designed to take advantage of the multiple paths
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is known as multithreaded applications. Windows NT was one of the first operating systems to
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take advantage of this technology.
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The Pentium also boasted a 64-bit data bus with a built-in math coprocessor. These machines
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also come with twin internal 8KB caches. One cache is used for data and the other is designed
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to store programming instructions.
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The first generation of Pentium processors did not double the external clock, whereas the
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econd generation had a clock multiplier of 1.5 or 3 depending on the model. Thus, the Pentiums
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ran from 33 to 200 MHz.
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Pentium Pro
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In 1995, the Pentium Pro was introduced. This processor was aimed at the higher-end servers
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and workstations. The Pentium Pro added a second memory-caching chip. This was the first
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Pentium that supported the Reduced Instrction Set Computer (RISC) processor. All of the other
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Pentiums only ran the Complex Instruction Set Computer (CISC) processor. Beacause a Pentium
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Pro was really a Pentium at heart, it also incorporated a CISC to RISC translator. Additional
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features like three-way superscalar execution and dynamic execution made this chip a powerhouse.
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Pentium MMX
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More and more applications began to rely on high-speed graphics. This manipulation was taxing
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even the fastest Pentium processors. To address this "need for speed" Intel released the third
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generation Pentium in 1997, which included a pipelined Multi-Media extension (MMX) chip. This
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provided a dedicated processor designed for Single Instruction Multiple Data (SIMD), which lets
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a single command operate on different sets of data.
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The SIMD feature of the MMX chip transformed the graphics industry, particularly in the games
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arena. In order to have the "latest and greatest," you had to have MMX. To upgrade to MMX,
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you needed to have a Pentium motherboard that matched the "socket 7" specification. The 233
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MHz MMX essentially ended the original Pentium line in June of 1997.
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Pentium II
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In 1997, the first Pentium with MMX built-in to the chip was introduced. This was the
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Pentium II. Thie chip added several features that revolutionized the processor market. These
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features included:
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- 512KB L2 cache in addition to the separate L1 caches that the Pentium already supported.
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- Error Correction Coding (ECC) of the L2 Cache bus, which ensured that the data being
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transported was checked and correct.
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- Single-Edge connector (SEC) packaging, which protected the internal circuitry and made the
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installation much easier and less prone to error.
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- Multiple branch prediction, which "looked-ahead" in the processing cycle and prefetched
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information along decision branches. This meant that when a decision was reached, the requested
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result was already loaded and ready.
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- Dual Independent Bus (DIB) design, which isolated the system bus from the cache bus. It
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allowed complete synchronization between the CPU and the various caches without being
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interrupted by any system calls.
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- Speculative execution, which executed operations based on "best-guess" results. This kept the
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pipes full and boosted system performance.
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- Data-flow analysis where the processor actually reorders the order of execution to ensure
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speedy processing. This required the CPU to actually analyze the instructional relationships
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between the different commands and avoid breaking the order too radically.
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Intel Celeron
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The consumer market was finally introduced to the speed increase of the microprocessor with the
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SX designation. The Pentium II was oriented more towards the business market, as the businesses
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were the only ones with the pockets deep enough to purchase Intel's powerhouse. To keep the
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revenue stream alive and provide the home consumer with more power, Intel introduced the Celeron.
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The Celeron was a pretty decent processor in comparison to other cloned processors on the market.
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It supported the MMX technology that was such a huge success in the home entertainment market.
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It also provided some of the Pentium II's sexier features, like multiple branch prediction,
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data-flow analysis, and speculative execution.
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Xeon
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The Xeon first became available in 1998 and soon became "the chip" for high-end servers. This chip
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supported a clock speed that ranged from 450 MHz to 1 GHz. The multiprocessing capabilites made
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this the prime choice for application servers where raw processing power is king. The Xeon
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designation was applied to the Pentium II and Pentium III chips to establish a CPU that was
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specifically designed for the server environment.
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Pentium III
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The Pentium III added streaming SIMD enhancements for mathematical processing and graphics rendering.
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It also provided additional support for power control, which allowed the processor to conserve
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power and generate less heat when in an idle state.
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Pentium 4
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The Intel Pentium 4 was designed for pure speed. The first Pentium boasted two pipelines, but the
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Pentium 4 has 20. It is a part of the Intel Netburst microarchitecture. Additional features
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include:
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- 400 MHz system bus that delivers 3.2GB per second to the memory controller.
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- Internal Arithmetic Logic Units that run at twice the clock speed.
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- Advanced dynamic execution that enhances the prediction of execution flow.
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- 128-bit, 144 instruction, streaming SIMD design for crisp, and more imporant, really fast graphics. |