Revisions J and earlier of the EtherTalk card have a timing problem with
Macintosh IIcx and Macintosh IIci units.
Symptoms of the problem are intermittent, and include: system hangs on
boot, serious system errors, and exceedingly poor network performance.
Revisions K and later of the EtherTalk card have been modified so that
they will not exhibit this problem.
The capacitance of a six-slot NuBus was factored into the timing
mechanism of the EtherTalk card. Consequently, the capacitance level in a
three-slot NuBus is lower, thereby effecting the EtherTalk card's timing.
As additional NuBus cards are installed into a system, the capacitance
level is raised on the NuBus. As a result, the problem is less likely to
present itself.
The most likely Macintosh IIcx and Macintosh IIci candidates for having
the symptoms mentioned above are units with a single EtherTalk card
installed and no other NuBus cards in the remaining two slots. This is a
configuration that would be commonly used for routers, file servers, mail
servers, and so on.
The only current solution is to use EtherTalk card revision K or later.