Re: proposal to fix ordering problem in PCI 2.1

[png@woof.net (Peter N. Glaskowsky)]

> We would like to sollicit comments on the proposal included below to
> modify the PCI protocol in order to fix a problem related to
> transaction ordering.

I think this is a bad idea. The scenarios described can be avoided without
adding such a painful extension to PCI. Only a single master should be
allowed (that is, eligible) to access a single PCI target address at any
one time. If multiple masters need to access the same target address, the
system should provide some other mechanism to arbitrate between them by
assigning "ownership" of the resource to one master at a time.

It seems to me that some of the scenarios described wouldn't necessarily
work right even if the proposed changes were made-- observers wouldn't
observe things consistently, multiple controllers wouldn't necessarily see
their commands executed in the right order, etc.

.                  png

ÆdR