38 lines
1.8 KiB
Plaintext
38 lines
1.8 KiB
Plaintext
=============================================================================
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AST RESEARCH, INC. TECHNICAL BULLETIN #0619 03-20-90
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=============================================================================
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RUNNING COMPATIBILITY TESTS ON THE VGA PLUS
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The IBM VGA standard supports two methods of addressing monochrome and color
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displays:
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- The VGA included on PS/2 systems allows software to address both
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monochrome and color monitors at the same time with no restrictions
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(colors in monochrome appear as shades of gray).
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- The VGA adapter for AT type systems allows software to address either
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color monitors or monochrome monitors, but not both.
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The AST VGA Plus adapter is compatible with the VGA standard for the IBM AT
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adapter. This means that software used with the VGA Plus will only address a
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color display in color mode or a monochrome display in monochrome mode.
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Switching between display modes is accomplished through the use of the
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ASTVGA.EXE utility included with the VGA Plus utilities.
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The adapter, by design, will not pass diagnostics written to test VGA
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monochrome modes while the adapter is in VGA color mode. In particular,
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tests from "PC Magazine" issue commands which are meant to test a PS/2 type
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adapter and will fail on an adapter which follows the IBM AT adapter
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standard. This is normal operation for any VGA adapter which follows the IBM
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AT VGA adapter standard.
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Some compatibility tests may also fail because of a hardware conflict. The
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IBM AT VGA adapter supports the use of hardware interrupt IRQ2. However, the
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AST VGA Plus adapter does not. The VGA Plus will fail tests such as one from
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"PC Tech Journal" (test 13) which attempts to use IRQ2.
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