QG80331M667 datasheet(35/67 Pages) INTEL

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Specification Update

Intel® 80331 I/O Processor

Non-Core Errata

48.

Bridge PCI ordering rule violation

Problem:

When the bridge is in PCI-to-PCI mode, it receives a downstream memory write which is claimed

by the bridge, followed by a subsequent memory read request which is enqueued immediately

afterwards. At the same time, the upstream buffers on the chip are filled with upstream Memory

Writes and read completion data. On the destination bus, the memory write is issued in small

fragments due to either target disconnect or a low setting of the secondary MLT, and the upstream

buffers begin to free up due to delivery of upstream Memory Write data. In between delivery of

downstream Memory Write fragments, the bridge issues the subsequent Memory Read, in violation

of PCI ordering rules.

Summary of the four failure modes:

1. PCI-to-PCI: A Memory Read transaction may pass a previously enqueued Memory Write.

2. PCI-to-PCI: A Configuration or I/O Read transaction may pass a previously enqueued

Memory Write.

3. PCI-to-PCI: A Configuration or I/O Write transaction (including type1 configure-to-special

cycle) may pass a previously enqueued Memory Write.

4. PCI-X-to-PCI: A Configuration or I/O Write transaction (including type1 configure-to-special

cycle) may pass a previously enqueued Memory Write.

Implication:

In the above scenario, a PCI read/write transaction can pass a PCI memory write transaction which

violates PCI ordering rules.

When the primary bus is PCI and secondary bus is PCI-X, this would only be seen as described in

item 4 listed above. No impact when the bridge is configured in PCI-X to PCI-X mode.

Workaround:

Use in PCI-X to PCI-X mode. When the primary bus is PCI and secondary bus is PCI-X, do not use

upstream DWORD I/O or type1 configure-to-special cycle writes that must be ordered against

previously issued Memory Writes.

Status:

Fixed. Fixed in D-0 stepping. See the Table , “Summary Table of Changes” on page 9.

49.

ATU claims PCI commands 8 and 9 when issued as Dual Address Cycle

(DAC)

Problem:

In PCI mode, commands 8 and 9 are reserved. The appropriate PCI response to these commands is

to master abort. When these commands are issued as a Dual Address Cycle (DAC), the Address

Translation Unit (ATU) claims them and they are executed as Memory Read (command 8) and

Memory Write (command 9) on the internal bus. The ATU properly master aborts SAC PCI

commands 8 and 9.

This issue does not occur in PCI-X mode.

Implication:

No negative impact expected, since these PCI commands are ‘reserved’ and should not be issued to

the ATU.

Workaround:

No workaround.

Status:

No Fix. Not to be fixed. See the Table , “Summary Table of Changes” on page 9.

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