[tulip-bug] Capture Effect

[Donald Becker]

On Tue, 3 Oct 2000, John William wrote:

> >> >From tulip	200 - 300 Kbytes/s
> >>To tulip	5 - 10    Mbytes/s
> >
> >This is what you should expect with a duplex mismatch.
> >"Don't do that."

> I am having a very similar problem with my tulip clone (FA310TX) card. My 

Which FA301TX card?  (Yes, there are several substantially different
versions).

> card is connected to a 10/100 switch as well. Both the switch and the card 
> indicate full duplex. The "tulip-diag" utility says the card is running FD. 
> But yet I still get a lot of frame errors on high receive load (none on 
> outgoing load). In my case, I get ~5.5MB/s from the card and 50-150K/s to 
> the card. Forcing half duplex on the card appears to work, in that the card 
> and switch indicate half duplex mode. The transfer rate problem (and framing 
> errors) doesn't change, however.

I'm guessing that you have a PNIC-I chip.

It appears that the PNIC-I is pretty picky about PCI bus timing.  Here is
what we think is happening: On some systems, with some slightly out-of-spec
PCI timing, the PNIC-I has a problem with receive FIFO synchronization.
This causes some receive packets to be corrupted and thus dropped.

The identical software load, adapter and network connection will work
without error on another motherboard.

The BSD driver has a work-around, but attempting to recover data from a
known-corrupted packet is pretty much like trying to save the food from a
broken glass jar.

> Maybe it's a bad interaction with the FA310TX card, but I can't believe 
> nobody would have noticed by now (since it is a fairly popular card). But in 
> any case, it's pretty easy to reproduce here so I think it is a driver 
> problem.

It might be easy for you to reproduce, but it's not easy to reproduce in
general.  Swap out your motherboard, leaving everything else the same, and
the problem will disappear.  These types of errors are very frustrating to
track down precisely.


Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993