
160
Registers
Chapter 4
AMD-8111 HyperTransport I/O Hub Data Sheet
24674
Rev. 3.00
April 2003
AMD Preliminary Information
Prefetching of the first, second, third or fourth cacheline as enabled by CPFEN_MR, CPFEN_MRL,
CPFEN_MRM only occurs when all of the following conditions are valid.
1. At least 1 internal PCI response buffer is available.
2. At least 1 internal HyperTransport command buffer is available.
The request address is smaller or equal to DevB:0x44[TOM] or DevB:0x44[ALLPF] = 1.
Default:
0000 0185h.
Attribute:
see below.
Bits
31:16 Reserved.
17
Reserved.
16
Reserved.
15:12
PDDTV. Prefetch data discard timer value.
Read-write. The discard timer for prefetch data expires
after PDDTV*2
6
+ 64 clock cycles. With the expiration of this timer all prefetch data is discarded.
(Revision C1 and later)
11
Reserved.
10:9
BLLIMIT. Burst length limit. .
Read-write. These bits specify how many cachelines are allowed to be
continuesly transfered to/from the external master. These bits apply to read and write bursts.
00 = no limitation
01 = 4 cachelines
10 = 8 cachelines
11 = 12 cachelines
If the burst length counter exceed these limits then the IC disconnects the transfer (even if in the read
case the next cacheline is available). Any prefetch operation stays unaffected.
8:6
[CPFEN_MRM, IPF_MRM].
These bits apply to memory read multiple requests. See bits 2:0.
5:3
[CPFEN_MRL, IPF_MRL].
These bits apply to memory read line requests. See bits 2:0.
2
CPFEN_MR. Continuous prefetch enable for memory read request.
Read-write.
1 =
One or more cachelines (up to three) of prefetch data is requested when a cacheline
starts to be transfered to the external master on the PCI bus. More cachelines are only requested if
the IPF count is not yet satis
fi
ed.
0 =
No cacheline of prefetch data is requested when a cacheline is transferred to the
master.
1:0
IPF_MR. Initial prefetch for memory read request.
Read-write. These bits specify how many
cachelines of prefetch data are requested upon an initial burst read request. This does not apply to
any burst read request that is retried because of a previous target disconnect.
00 =
1 cacheline
01 =
2 cachelines
10 =
3 cachelines
11 =
4 cachelines
Description