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CHAPTER 4
CHAPTER 4
CHAPTER 4
CHAPTER 4
CHAPTER 4
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
®
at PIIX4
Passive Release) while transferring control information or data for
USB transaction. During Disabled, PIIX4
without using passive release.
®
PIIX4
Passive Release
The PIIX4
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
®
when the PIIX4
PCI is immediately retrieved 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.
®
ISA bridge support GAT (Guaranteed Access Time)
®
is the target of a PCI transaction. A read cycle from Host to
®
AMI
AMI
AMI
BIOS USER'S GUIDE
BIOS USER'S GUIDE
BIOS USER'S GUIDE
AMI
AMI
BIOS USER'S GUIDE
BIOS USER'S GUIDE
®
to use passive release(look
®
will perform PCI accesses for USB
delay transaction mechanism is enabled
4-14
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