AMD-751 Datasheet, PDF (6/14 Pages) Advanced Micro Devices – AMD-751-TM System Controller Revision Guide

Preliminary Information
AMD-751™ System Controller Revision Guide
22564B-1—February 2000
1
Invalid Read Performed After a Slave PCI Target Abort
Products Affected. C3 and C5
Description. When the AMD-751 system controller initiates an unaligned doubleword PCI I/O read
transaction and this I/O read receives a target abort from the PCI slave, the next PCI I/O read returns
incorrect data. Aligned transactions are unaffected.
Potential Effect on System. A target abort on the PCI bus is an extremely rare event and the occurrence of
the abort is considered a catastrophic error condition. This condition was artificially created for PCI
testing and has not been observed in normal system validation testing.
Suggested Workaround. None
Resolution Status. Fixed in a future revision of the AMD-751 system controller.
2
Arbitration Latency Due to No Bus Preemption
Products Affected. C3
Description. The AMD-751 PCI arbiter can impose long latencies on external PCI bus masters when any
master that currently owns the bus is attempting long transfers due to not correctly supporting bus
preemption. When a PCI master’s bus grant is active and another master requests the bus, the arbiter
should immediately deassert the grant to the first master, thus preempting the first master. The first
master is permitted to continue bus transactions for the duration of its master latency timer. Due to
the anomaly in the arbiter, the original master does not get preempted if it owns the bus and it
continues to keep its request pin asserted. Therefore, it could use the bus indefinitely. However, this
problem has not been seen with any real system hardware and software.
Potential Effect on System. Some peripherals may experience timeouts. A lack of fairness on the bus.
Suggested Workaround. None
Resolution Status. Fixed in Rev C5.
4