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CHAPTER 3
AMI
®
BIOS USERS GUIDE
AGP 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 forwarded 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 4MB, 8MB, 16MB, 32MB, 64MB, 128MB, and 256MB.
USB Passive Release
During Enabled, this will allow the PIIX4® to use passive
release(look at PIIX4® Passive Release) while transferring control
information or data for USB transaction. During Disabled, PIIX4®
will perform PCI accesses for USB without using passive release.
PIIX4® Passive Release
The PIIX4® ISA bridge support GAT (Guaranteed Access Time)
mode, which will now violate the spirit of the PCI specification. The systems
provides a programmable passive release mechanism to meet the required
master latencies. During Enabled, ISA masters may see long delays in
accessing PCI memory, including the main DRAM array. The ISA GAT mode
is also not supported during enable. ISA masters must honor IOCHRDY.
PIIX4® Delayed Transaction
During Enabled, the PIIX4® delay transaction mechanism is
enabled when the PIIX4® is the target of a PCI transaction. A read cycle
from Host to PCI is immediately retrived due to any pending PCI to DRAM
cycle. During Disabled, a read cycle from Host to PCI is waited until time-
out due to any pending PCI to DRAM cycle.
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