Michael T. Stolarchuk writes:
 > 
 > 
 > As for switching into half duplex; we've been running half duplex
 > with the 21143/de500's and have had the same performance problems.
 > The cards work fine for casual use, but once you try to push the
 > network, they 164LX 533 MHz seem to cause too many collisions.

We also see lots of collisions (a rate of about 2.5%), but its not bad 
enough to impact performance seriously.

 > 
 > Is there another device, for example, fxp's which do reliably swith
 > into 100mb-fdx ?

The only cards I've seen this problem with is the 21143s.  We have
dozens of PCs, including a few NFS servers, which work reliably in
full-duplex mode with with fxps (under FreeBSD). I haven't tried an
fxp in an alpha.  

Older tulips (we have a batch of no-name 21140A cards in some older
alphas & PCs here) also work reliably in full-duplex mode.

Drew