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82815 GMCH
R
Datasheet
133
4.4.
Host Interface
The host interface of the GMCH is optimized to support the Intel
Pentium
III
processor,
Intel
Pentium II processor, and Intel
Celeron
TM
processor. The GMCH implements the host address,
control, and data bus interfaces within a single device. The GMCH supports a 4-deep in-order queue
(i.e., supports pipelining of up to 4 outstanding transaction requests on the host bus) . Host bus addresses
are decoded by the GMCH for accesses to system memory, PCI memory ane PCI I/O (via hub interface),
PCI configuration space, and graphics memory. The GMCH takes advantage of the pipelined addressing
capability of the processor to improve the overall system performance. The GMCH supports the 370-pin
socket processor connector.
4.4.1.
Host Bus Device Support
The GMCH recognizes and supports a large subset of the transaction types that are defined for the Intel
Pentium
III
processor, Intel
Pentium II processor, or Intel
Celeron
TM
processor bus interface. However,
each of these transaction types have a multitude of response types, some of which are not supported by
this controller. All transactions are processed in the order that they are received on the processor bus.
Table 10. Summay of Transactions Supported By GMCH
Transaction
REQa[4:0]#
REQb[4:0]#
GMCH Support
Deferred Reply
0 0 0 0 0
X X X X X
The GMCH will initiate a deferred reply request for a
previously deferred transaction.
Reserved
0 0 0 0 1
X X X X X
Reserved
Interrupt
Acknowledge
0 1 0 0 0
0 0 0 0 0
Interrupt acknowledge cycles are forwarded to the hub
interface.
Special
Transactions
0 1 0 0 0
0 0 0 0 1
See separate table in special cycles section.
Reserved
0 1 0 0 0
0 0 0 1 x
Reserved
Reserved
0 1 0 0 0
0 0 1 x x
Reserved
Branch Trace
Message
0 1 0 0 1
0 0 0 0 0
The GMCH will terminate a branch trace message without
latching data.
Reserved
0 1 0 0 1
0 0 0 0 1
Reserved
Reserved
0 1 0 0 1
0 0 0 1 x
Reserved
Reserved
0 1 0 0 1
0 0 1 x x
Reserved
I/O Read
1 0 0 0 0
0 0 x LEN#
I/O read cycles are forwarded to hub interface. I/O cycles
that are in the GMCH configuration space are not forwarded
to the hub interface.
I/O Write
1 0 0 0 1
0 0 x LEN#
I/O write cycles are forwarded to hub interface. I/O cycles
that are in the GMCH configuration space are not forwarded
to the hub interface.
Reserved
1 1 0 0 x
0 0 x x x
Reserved
Memory Read &
Invalidate
0 0 0 1 0
0 0 x LEN#
Host initiated memory read cycles are forwarded to DRAM
or the hub interface.
Reserved
0 0 0 1 1
0 0 x LEN#
Reserved