There are several potential causes for problems with AppleShare PC and 3COM
EtherLink II cards.
The most common is attempting to use Phase 1 services (usually after upgrading
from AppleShare PC 1.x to AppleShare PC 2.0.x). Since AppleShare PC 2.0.x is
Phase 2 only, you can only use it with Phase 2 services unless a router with
both Phase 1 and Phase 2 drivers is present.
The card model is also important. 3COM has produced at least three different
PC or AT bus Ethernet cards, all with the name EtherLink II. We are familiar
with models 501, 503, and 505. The model 501 is an 8-bit card, quite old, and
not supported. The model 503 is the most common, and what we wrote our
EtherLink II MLID for. The model 505 arrived later and is a 16-bit card (AT
bus only). We do not yet support this card. The 503 driver will not work
with it because the model 505 is substantially more complex and full-featured.
Another reason could be that they are trying to load 3COM-supplied drivers
before loading AppleShare PC. This does not work. It prevents AppleShare PC
from communicating with the network. Installing NetBIOS support will have the
same effect.
Finally, the ENET3CII driver has problems when the bus speed of the PC is over
8MHz. The CPU speed can be greater, but the expansion bus speed cannot be
above 8MHz. This is rarely a problem, but could be if you shift the PC into
its non-turbo mode and things work.