Hi,
I need some help with a pci/pci bridge (a dec 21152 rev 0x3).
This is the bridge which is on the new 4 ports Dlink 580. There
are 4 sundance (ste) chips behind it.

Here is my problem: when nly one ethernet port is used, no problems,
I get 100Mb/s full-duplex.
If I try to route between 2 ports and start a ttcp between 2 hosts routed
by it, there are packet loss at RX time (only on the side which receive
the large paquets). From investigation this seems to be rx overrruns,
that is, the sundance can't write data to RAM fast enouth.

If I add SMC etherpower II, and use it and only one port of the DFE580,
I get the same problem. It doesn't show any improvements at all, so it's not
contention on the bus behind the pci/pci bridge. It seems to be the bridge
itself which misbehaves.

I have another adapter (from compaq, with 2 sym875 and a tulip) with the exact
same bridge, which behaves well in a alpha ds20, so I know this bridge can
be efficient.

I tried different settings for the RX thresholds in ste, but this doesn't
help.
I started frobbing with registers on the bridge, but I'm running out of idea.
I tried increasing the latency timer up to 0xc0, on both the ste and the
bridge, without success.
Does anyone have an idea on what to try ? Does anyone know if PCI-PCI bridges
have parameters for fifos ?

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
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