Riser card -mainboard conflicts?

[tegner at nada.kth.se]

Hi all!

We have a cluster consisting of 30 athlon 2000+ nodes on a KT3 Ultra
MS-6380E mainboard (using ide discs) connected by a fast Ethernet
network.

For the nodes we use 2U chassis, and the NIC and the graphic card sit on a
PCI-301 riser card.

We are experiencing odd problems;

On one of the nodes we can newer get the network to function, there
are messages about bus-master dirty, PCI bus error, etc, and we never
get any contact with the rest of the cluster.

The other nodes "seem" to work OK, but for some parallel applications
one or more of the nodes just "give up" after some time, and in those
cases we get similar messages as above - but it have also happened
that a node just died in which case we have to use the reset button to
get it back.

We start to suspect that mainboard and the riser card are in some way
incompatible, but we would greatly appreciate any hints of other
reasons for these problems.

/jon