22 May
1997
22 May
'97
4:50 a.m.
I agree that this is a good idea, as many of these
chips will be quite
rare in the future. I must add that trying to crack the logic of a chip
larger than a simple PAL would be a serious task. Simple 1000 gate ASICs
would be next to impossible. Even for classic computers, a 1000 gate ASIC
is small.
It depends on how much you already know about the functionality of the
chip. If you have the service manual that describes what the chip is for,
and roughly what the external signals are, then often a logic analyser
will give you enough info to recreate the chip. If you have no idea what
the chip is for, then you probably haven't a hope of decoding it.
By all means, try to read out the contents of PALs -
many never have
their protection bits turned on. Blank PALs are plentiful (stock up on
them now!) - burn a replica and see if it works.
You can replace most PALs with correcly programmed GALs, which are still
being made AFAIK. This may not be historically correct, but it will get
the machine running again.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill