SMC EtherPower and a switch

[George]

I have an SMC EtherPower I with a true Digital chip that has worked great
one a 10baseT hub for years now.  I recently changed to a 10/100 switch and
have experienced network link loss under computer load.  It seems whenever
I load the processor, the Ethernet card loses link with the switch
intermittantly. Doing an FTP inbound then becomes a bursty 200 Mbit as the
link drops every few seconds and stays down a few seconds before coming
back up.  I ran only rc5des on the machine and couldn't get into it until a
few hours later when my 'ssh host killall rc5des' actually survived the
90%+ packet loss (from a machine connected to the same switch).  Network
traffic was normal after it was killed.

The offending card (SMC EtherPower) is a Digital DC21140-AC chip on a Tyan
Tomcat IV SMP motherboard with 2 Pentium 233MMX's and a 16-port D-Link
switch. DSS-16+.  I've tried the stock Linux 2.2.10 v0.89H 5/23/98
and the development v0.91e 5/27/99 driver without a difference

  Bus  0, device  20, function  0:
    Ethernet controller: DEC DC21140 (rev 32).
      Medium devsel.  Fast back-to-back capable.  IRQ 16.  Master Capable.
Latency=32.  Min Gnt=20.Max Lat=40.
      I/O at 0x6100 [0x6101].
      Non-prefetchable 32 bit memory at 0xe0000000 [0xe0000000].

Doing 100 Mbit HD/FD FTP drops the link by itself.  A 10 Mbit HD/FD FTP
doesn't drop the link by itself.

Another card (NetGear FA310-TX) with a Digital DS21140-AE on the same
motherboard/processor pair (my desktop) works just fine on the same model
but different switch, it is 5 port model, DSS-5+.

  Bus  0, device  20, function  0:
    Ethernet controller: DEC DC21140 (rev 34).
      Medium devsel.  Fast back-to-back capable.  IRQ 16.  Master Capable.
Latency=32.  Min Gnt=20.Max Lat=40.
      I/O at 0x6100 [0x6101].
      Non-prefetchable 32 bit memory at 0xe4002000 [0xe4002000].

The latter card FTP'd a 693,951,150 byte file to /dev/null via FTP on an
NFS root mounted drive without trouble.  It completed:

693951150 bytes received in 422 secs (1.6e+03 Kbytes/sec)

Speed isn't really representative of card capability as my machine had to
send the file out via NFS so the other machine could send it back via FTP.

Ideas?

-George Greer