DOCUMENT:Q102956  26-AUG-1993  [W_NT]
TITLE   :ATI Graphics Ultra Pro or Plus Defaults to VGA
PRODUCT :Windows NT
PROD/VER:3.10
OPER/SYS:WINDOWS
KEYWORDS:

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 The following information applies to:

  - Microsoft Windows NT operating system version 3.1
  - Microsoft Windows NT Advanced Server version 3.1
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SUMMARY
=======

If your computer has an ISA bus and more than 12 MB of system RAM
installed with the Graphics Ultra Pro or Plus, the Memory Aperture
feature must be disabled.

NOTE: Disabling the Memory Aperture feature can cause noticeable
video performance degradation.

You can disable the Memory Aperture feature with the ATI-supplied
INSTALL.EXE program. If you are unable to disable the Memory Aperture
feature, type "TEST.COM /i" (do not enter the quotation marks and make
the letter "i" is in lowercase) to initialize the Graphics Ultra Pro
or Plus. Then run the ATI-supplied INSTALL.EXE program and disable the
Memory Aperture feature, save the settings, and reboot the system.

MORE INFORMATION
================

The Memory Aperture feature on the Graphics Ultra Pro and Plus
products moves the video frame buffer into the motherboard system
memory address space to improve performance. While not required to
access the color and resolution capabilities of these graphics
accelerator products, it does improve performance.

386- and 486-based ISA systems use a 32-bit bus dedicated to system
RAM in order to address more than 16 MB of memory. Adapter cards,
however, are restricted to the addressing capabilities of the bus
architecture. The 16-bit ISA bus has a physical limitation that
restricts its addressing capabilities to a maximum of 16 MB of RAM.

The 2 MB Memory Aperture feature on the Graphics Ultra Pro and Plus
must be placed at a memory interval of at least 2 MB above the last
address in system memory. Therefore,

   system memory (up to 12 MB) + system memory interval (2 MB) + 
   Graphics Ultra Pro Memory Aperture (2 MB) = no more than 16 MB

NOTE: The above restriction also applies to EISA-bus-based 386 and 486
systems with an ISA Graphics Ultra Pro or Plus installed. The EISA
Graphics Ultra Pro and Plus does not have this problem.

Graphics Ultra Pro and Plus are manufactured by ATI, a vendor
independent of Microsoft; we make no warranty, implied or otherwise,
regarding these products' performance or reliability.

Additional reference words: 3.10 crash vga slow
KBCategory:
KBSubCategory:

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Copyright Microsoft Corporation 1993.