Intel 82925X, Datasheet

Page: 127 / 242

Host-PCI Express* Graphics Bridge Registers (D1:F0)
R
Intel
®
82925X/82925XE MCH Datasheet 127
Bit Access &
Default
Description
2 R/W
0b
ISA Enable (ISAEN): This bit is needed to exclude legacy resource decode to
route ISA resources to legacy decode path. This bit modifies the response by the
MCH to an I/O access issued by the processor that target ISA I/O addresses.
This applies only to I/O addresses that are enabled by the IOBASE and IOLIMIT
registers.
0 = All addresses defined by the IOBASE and IOLIMIT for processor I/O
transactions will be mapped to PCI Express Graphics.
1 = MCH will not forward to PCI Express Graphics any I/O transactions
addressing the last 768 bytes in each 1-KB block, even if the addresses are
within the range defined by the IOBASE and IOLIMIT registers. Instead of
going to PCI Express Graphics, these cycles are forwarded to DMI where
they can be subtractively or positively claimed by the ISA bridge.
1 R/W
0b
SERR Enable (SERREN)
0 = No forwarding of error messages from secondary side to primary side that
could result in an SERR.
1 = ERR_COR, ERR_NONFATAL, and ERR_FATAL messages result in SERR
message when individually enabled by the Root Control register.
0 RO
0b
Parity Error Response Enable (PEREN): This bit controls whether or not the
Master Data Parity Error bit in the Secondary Status register is set when the
MCH receives across the link (upstream) a Read Data Completion Poisoned
TLP.
0 = Master Data Parity Error bit in Secondary Status register cannot be set.
1 = Master Data Parity Error bit in Secondary Status register can be set..