RE: PCI system integration issues

["Brian Small" <small@quicklogic.com>]

Ben,

Make sure that the problem is not in the stuff behind your AMCC chip on your
plug in card.

What might happen, for example, is that the memory controller might cause
the transaction to happen more slowly with more wait states or retries, thus
causing a FIFO behind the AMCC device to fill up or overflow on PCI writes,
or underflow on pci reads, revealing a previously undiscovered bug in the
card design.

Very often the PCI controller is thought to be the problem in such
circumstances, when it is not.

- Brian

> -----Original Message-----
> From: Ben Yurick [mailto:byurick@keithley.com]
> Sent: Thursday, May 04, 2000 10:54 AM
> To: 'PCI SIG email reflector'
> Subject: PCI system integration issues
>
>
>
> Hello, while we are on the AMCC topic, my company has a
> couple products
> that
> use the AMCC S5933QE PCI interface chip. We are experiencing very
> strange behavior
> with these products. One particular PCI card that uses the
> AMCC does bus
> mastering DMA
> from onboard hardware FIFOs to the PC's memory. This card fails
> busmastering at the device
> driver level occasionally. So far we can't make sense of this. I have
> replaced the AMCC with the
> 5935QF LSI and it did not help. What we see are failures in some
> operating systems and not others.
> For example, the card works fine in a Windows NT system with a 440BX
> chipset but it will _sometimes_
> fail in a windows 95 system with a via chipset. We have also seen
> fail/pass inconsistencies when moving
> it around on different PCI slots. We have several different device
> drivers to talk to the card as well. We also
> see variability there.. some device drivers will show busmastering
> failures others will run the card successfully
> forever. The system as a whole has me baffled. I examined the PCI
> busmaster transactions in the failing systems
> and see no PCI violations. The 5933/5935 always does transfers
> correctly. It will always do passthru transfers
> correctly also.
>
>     Is anyone aware of these kinds of system level issues with PCI
> devices with respect to the practically infinite
> combinations of PCI BIOS's, chipsets, operating systems,
> device drivers,
> etc? I would like to pin down
> what the offenders are so I know if we need to go redesign our card.
> There are many systems that our card
> runs flawlessly in so I hesitate. My company is setup so that our
> product get to run in many different computer combinations
> as our software drivers are developed. Almost every PCI product so far
> has some kind of a problem in certain
> systems and not others. It is frustrating because I dont know what to
> debug/fix if I cant pin down what is wrong and
> so far, there is no pattern as to what combinations do not play well
> together. I would like to say it is our design, but
> how can it work flawlessly in some systems? Also some of our
> design are
> so simple, it could really only be the 5933
> responsible and I cant blame that either!
>
> How can a software driver do busmastering successful sometimes and not
> others in same power cycle?
>
> How can Operating system be cause bus mastering failures sometimes and
> not others?
>
>
> Please anybody with some advice or suggestions please respond.
> I would be very thankful to anyone who could provide
> some insight! Thanks!
>
>
> Ben Yurick
> Design Engineer
> Keithley Instruments
> (440)498-2871
>
>