ATI Graphics Ultra Pro or Plus Defaults to VGA

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

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 sure the letter "i" is 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

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.