I've got an old 3Com etherlinkII card, with the 3C509/3C509b chipset. The thing works fine under winblows, but I'm not sure how to set it up under Linux, since pnpdump won't detect it (evidently winblows switched off pnp for the card). What commands do I need to feed the shell (I know the card's IRQ and DMA) to get it hopping? I'm trying to turn this box into a router, so this'll be eth1.

Thanks!

Is it an ISA card then?

Yes, it is indeed an ISA card, I believe with pnp deactivated (and none of those nice little dipswitches either). Apparently this chipset works a little differently than other ISA cards.

I had the same trouble. This is where you need to find the module and load it manually. I do not know why this is not found by the OS! but there is a module for the Etherlink III.
My problem was finding what the module was called. I think I found it in a book in the end and it wasnt what I expected it to be.
Once it had loaded I could configure the IP details no problem. The next problem was the OS finding the card on a reboot!
I then ran into more serious problems elsewhere and didn't manage to fix that. Although a script in the start up would have sorted it out.
Sorry I cant remember the module name. Its something like 3c509B. So to load
# insmod 3c509B

There is a way to search for the modules on your system that can be used.

Have you tried the isapnp command?
Read about it in the man pages, man isapnp
I haven't tried this my self, at least not recently.