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ATI graphics +/Pro Technical Note No. 67 - Memory Aperture configuration issues.
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ATI graphics +/Pro Technical Note No. 67 – Memory Aperture configuration issues.
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ATI Technologies Inc.,

3761 Victoria Park Avenue,
Scarborough, Ontario, M1W 3S2

Tel:(416) 756-0718 Fax:(416) 756-0720
Telex:06-966640 (ATI TOR)

Technology you can Trust

Customer Support Department
Technical Note No. 67 - Mach 32 Memory Aperture Configuration

January 18, 1993


The following information describes common configuration issues
which may arise when configuring the Memory Aperture feature of
the Graphics Ultra Pro or Graphics Ultra + video adapter.


The Memory Aperture feature, on the Graphics Ultra Pro/+
products, is an option which 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 the Graphics Accelerator product, some
ATI drivers and utilities make reference or use of the memory

Memory Aperture Failures

1). If your computer has an ISA BUS and more that 10 Mb of
system RAM installed, the Graphics Ultra Pro/+ Memory
Aperture Feature cannot be enabled.

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 resticted 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 4 Mb memory aperture feature on the Graphics Ultra Pro/+
must be placed at a memory interval of at least 2 Mb above
the last address in system memory. Therefore, SYSTEM MEMORY
ULTRA PRO MEMORY APERTURE (4 Mb) = No more than 16 Mb.

Customer Support Department
Technical Note No. 67 - Mach 32 Memory Aperture Configuration

If the MEMORY APERTURE FEATURE has been enabled in this
situation, it must be disabled with the ATI supplied
INSTALL.EXE program. If you are unable to disable the
memory aperture feature, run the ATI supplied "TEST.COM /i"
(do not enter the quotation marks, the letter "i" must be in
lower case) to initialize the Graphics Ultra Pro/+. Then run
the ATI supplied INSTALL.EXE and disable the memory aperture
feature, save the settings and reboot the system.

*NOTE: The above will also apply to EISA BUS based 386 and 486
systems with an ISA Graphics Ultra Pro/+ installed. The EISA
Graphics Ultra Pro/+ does not apply.

2). Memory diagnostics, in the TEST program, will fail if a
secondary MDA or CGA video card is installed in the system
with the Graphics Ultra Pro/+. When an 8 BIT MDA or CGA
video card is detected, the Graphics Ultra Pro/+ is placed
into an 8 BIT addressing mode to comply with system
addressing standards. In an 8 BIT mode the maximum
addressable memory is 1 Mb and, therefore, the entire memory
aperture would not be addressable. In this configuration
the memory aperture must be disabled.

3). Incorrect motherboard DIP SWITCH or JUMPER settings, which
indicate the amount of system memory installed, will cause
the Memory Aperture Feature to fail. While not all
motherboards contain memory configuration jumpers or
switches, incorrect settings will cause installation or
diagnostic errors. If your system has 8Mb of RAM installed
and the motherboard DIP switches are set to 16 Mb, the
memory aperture feature on the Graphics Ultra Pro/+ will not
function correctly. Check your motherboard manual for
correct settings.

4). Even though DISABLED, the Installation software may report a
conflict between the memory aperture and main system memory.
This error usually appears when saving configuration changes
in the INSTALL software in systems containing 16 Mb or more
of memory. Run the TEST program to ensure that the Graphics
Ultra PRO/+ is functioning properly and, if so, ignore the
warning message. The Graphics Ultra Pro/+ will operate
properly in this configuration. The Memory Aperture Feature
is NOT required to run Windows (with Build 48 or higher) or

2 ACCESS : all

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