MSI 815 PRO Manual page 59

Video BIOS Cacheable
Select Enabled allows caching of the video BIOS , resulting in better
system performance. However, if any program writes to this memory area, a
system error may result. The settings are: Enabled and Disabled.
Memory Hole At 15M-16M
You can reserve this area of system memory for ISA adapter ROM.
When this area is reserved, it cannot be cached. The user information of
peripherals that need to use this area of system memory usually discusses
their memory requirements. The settings are: Enabled and Disabled.
CPU Latency Timer
During Enabled, A deferrable CPU cycle will only be Deferred after it
has been in a Snoop Stall for 31 clocks and another ADS# has arrived.
During Disabled, A deferrable CPU cycle will be Deferred immediately after
the GMCH receives another ADS#.
Delayed Transaction
The chipset has an embedded 32-bit posted write buffer to support
delay transactions cycles. Select Enabled to support compliance with PCI
specification version 2.1. The settings are: Enabled and Disabled.
On-Chip Video Window Size
This option allows the user to set the on-chip video window size
for VGA driver use.
AGP Graphics Aperture Size
This option determines the effective size of the graphics aperture
used in the particular PAC configuration. The AGP aperture is memory-
mapped, while graphics data structure can reside in a graphics aperture. The
aperture range should be programmed as not cacheable in the processor
cache, accesses with the aperture range are forwaded to the main memory,
then PAC will translate the original issued address via a translation table that
is maintained on the main memory. The option allows the selection of an
aperture size of 32MB, 64MB.
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