13 Sep
2013
13 Sep
'13
2:57 p.m.
Given that
there was already a bad joint on the replacement socket, I
wonder if there's other damage.
Possibly. The socket does correspond to the bad bit in the Sad Mac
code, so one of my thoughts is that they saw the code, tried to replace
the chip and the problem did not go away and the board was shelved. Have you tried 'buzzing out' all the pins
on the socket (and other RAMs
if you want to be sure) to wherever they should go (address muxes, data
bus, timing/control PALs). My first guess would be an open connection
somewhere.
I have buzzed the socket to adjacent DRAMs and the 14 common pins
all buzz fine. I have not walked Din and Dout everywhere (yet).