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©2008 Advanced Micro Devices, Inc.
Host PCI Bridge Registers (Device 20, Function 4)
AMD SB600 Register Reference Manual Proprietary Page 275
Prefetch Size Control - 32 bits - [PCI_Reg: 60h]
Field Name Bits Default Description
Read Size 2:0 2h If prefetch function is enabled, this defines the number of
initial prefetch cachelines for a PCI READ command
Read Size Adjustment 3 1b When set, PCIBridge will adjust the prefetch size for READ
automatically. If this bit is 0, then the prefetch size is always
defined by bits [2:0]
Read Line Size 6:4 4h If prefetch function is enabled, this defines the number of
initial prefetch cachelines for a PCI READLINE command
Read Line Adjustment 7 1b When set, PCIBridge will adjust the prefetch size for
READ_LINE automatically. If this bit is 0, then the prefetch
size is always defined by bits [6:4]
Read Multiple Size 10:8 6h If prefetch function is enabled, this defines the number of
initial prefetch cachelines for a PCI READ_MULTIPLE
command
Read Multiple
Adjustment
11 1b When set, PCIBridge will adjust the prefetch size for
READ_MULTIPLE automatically. If this bit is 0, then the
prefetch size is always defined by bits [10:8]
Prefetch Size Lower
Limit
14:12 0h The lower limit of the adjusted prefetch size.
Reserved 15 0b
Prefetch Size Upper
Limit
18:16 7h The upper limit of the adjusted prefetch size.
Reserved 19 0b
Prefetch Size Mlt
Enable
20 1b This also controls how PCIBridge adjusts the auto-prefetch
size. When set, PCIBridge will only adjust the prefetch size
if it knows it does not have enough or has too much data in
the prefetch buffer. Recommendation is to always set this
bit.
Reserved 31:21 0h
The fields in this register are effective only when prefetch is enabled (reg0x64[7]=1).
Misc Control Register - 32 bits - [PCI_Reg: 64h]
Field Name Bits Default Description
Downstream Config
Cycle Flush Enable
0 0h When this bit is 1, any downstream config cycle will flush all
the upstream read prefetch buffers.
Downstream Write
Cycle Flush Enable
1 1h When this bit is 1, any downstream non-config write cycle
will flush all the upstream read prefetch buffers.
Downstream Read
Cycle Flush Enable
2 0h When this bit is 1, any downstream non-config read cycle
will flush all the upstream read prefetch buffers.
Prefetch Buffer Timeout
Enable
3 1h When this bit is 1, upstream read prefetch buffer timeout
mechanism is enabled. If data stay in a buffer longer than
the time specified in Prefetch Timeout Limit (Reg5Ch), the
buffer will be flushed.
AB Masking Prefetch
Request Enable
4 1h The purpose of this is to improve the internal bus efficiency
and the recommendation is to have it set to 1
AB Masking Non-
prefetch Request
Enable
5 1h The purpose of this is to improve the internal bus efficiency
and the recommendation is to have it set to 1
Downstream Cycle
Flush Control
6 0h 0—If a downstream cycle is qualified to flush upstream
prefetch read buffer (depending on bit[2:0] in this register),
the flush happens when the cycle is sent out onto PCI bus
with at least one data phase..
1—If a downstream cycle is qualified to flush upstream
prefetch read buffer (depending on bit[2:0] in this register),
the flush happens as soon as the cycle arrives at PCI bus.