Macintosh IIfx: Logic Board Jumper Settings


A customer's Macintosh IIfx is not functioning, and I suspect that the
jumper settings on the logic board have been altered. What should I check
for?

Jumper J103 on the Macintosh IIfx logic board disables the external 68030
RAM cache when it is disconnected. In the event that the jumper is
removed, the system may not reset properly when turned on, essentially
disabling the system.

As a side note, the jumper next to J103, J106, is used for debugging. This
jumper is not documented because it can severely affect system
performance.


Published Date: Feb 18, 2012