Re: Information on 64-bit PCI

["Monish Shah" <monish.shah@indranetworks.com>]

> Hi all,
> We have a 64-bit PCI  card with PLX9656. In order to
> test the 64-bit support of our card,we installed our
> card on a 64-bit PCI Slot with the Machine details as
> below :

...


> Here is our observations:
>
> 1) While booting we are getting a REQ64# and for which
> there is no ACK64#.

This is probably happening while reset is asserted.  This is part of the PCI
spec and it is meant to allow cards to detect the presence of a 64 bit host.
(I'm going by memory here - look at the PCI spec if you want the details.)

> 2)When we write a 64-bit value to a location in SRAM,
> We observed that in a single SRAM_CS(Chip Select) we
> are observing two(2)SRAM_WR(write). If we read the
> written 64-bit value, we are observing
> two(2)SRAM_RD(Read) in a single SRAM_CS. Note that we
> are not getting any signal on ACK64# and REQ64# pin.

For a single 64 bit transaction, the host bridge probably does not bother to
assert REQ64.  The reason is that it will not improve performance.  You can
save one data phase, which would save 1 cycle, but you would waste a cycle
in REQ64 / ACK64 protocol.  Again, I'm going by memory, so some details
could be missing.

> >From the above we are unable to conclude that our card
> support 64-bit transaction.

Try doing long DMA transactions.  You should see 64 bit transactions in that
case.

> Can anyone please guide us in this regard.
>
>
> Hoping for a faster response.
>
> Thanks in advance.
> Ashwin.T.V

Monish Shah
Indra Networks