82815 GMCH
R
134
Datasheet
Transaction
REQa[4:0]#
REQb[4:0]#
GMCH Support
Memory Code
Read
0 0 1 0 0
0 0 x LEN#
Memory code read cycles are forwarded to DRAM or the
hub interface.
Memory Data
Read
0 0 1 1 0
0 0 x LEN#
Host-initiated memory read cycles are forwarded to DRAM
or the hub interface.
Memory Write
(no retry)
0 0 1 0 1
0 0 x LEN#
This memory write is a writeback cycle and cannot be
retried. The GMCH forwards the write to DRAM.
Memory Write
(can be retried)
NOTES:
1. For Memory cycles, REQa[4:3]# = ASZ#. GMCH only supports ASZ# = 00 (32 bit address).
2. REQb[4:3]# = DSZ#. DSZ# = 00 (64 bit data bus size).
3. LEN# = data transfer length as follows:
LEN#
Data length
00
<= 8 bytes (BE[7:0]# specify granularity)
01
Length = 16 bytes BE[7:0]# all active
10
Length = 32 bytes BE[7:0]# all active
11
Reserved
0 0 1 1 1
0 0 x LEN#
The standard memory write cycle is forwarded to DRAM or
the hub interface.
Table 11. Host Responses Supported by the GMCH
RS2#
RS1#
RS0#
Description
GMCH Support
0
0
0
idle
0
0
1
Retry Response
This response is generated if an access is to a resource
that cannot be accessed by the processor at this time and
the logic must avoid deadlock . Hub interface directed
reads, writes, and DRAM locked reads can be retried.
0
1
0
Deferred
Response
This response can be returned for all transactions that can
be executed ‘out of order.’ Hub interface directed reads
(memory, I/O and Interrupt Acknowledge) and writes (I/O
only), and internal Graphics device directed reads
(memory and I/O) and writes (I/O only) can be deferred.
0
1
1
Reserved
Reserved
1
0
0
Hard Failure
Not supported.
1
0
1
No Data
Response
This is for transactions where the data has already been
transferred or for transactions where no data is
transferred. Writes and zero length reads receive this
response.
1
1
0
Implicit
Writeback
This response is given for those transactions where the
initial transactions snoop hits on a modified cache line.
1
1
1
Normal Data
Response
This response is for transactions where data accompanies
the response phase. Reads receive this response.