Tried a couple of old ISA bus NICs--a "Simple Net SN2000CT" and an "E2000plus". The SN2000CT gives "invalid signature 30 30" errors during boot, and the e2k almost works, but lots of "mismatched read page pointers" and "timeout waiting for Tx RDC" errors.
Both cards were set to 0x300/IRQ3. Each was tested in normal configuration, with the SBHE pin pulled to gnd, with SBHE pulled to +5, and with tape applied over the card's 16 bit ISA connector section. I also tried re-running the dos setup programs for each card once I'd applied the tape (thinking I could force the configuration to 8 bit only mode). The SimpleNet setup program detected this and reset the card to 8 bit mode, the E2k setup program didn't see the card at all. Even after all this, the SN card still failed with invalid signature.
Guess I'll have to order a couple of those $5 surplus NICs afterall...
