21 May
1997
21 May
'97
3:47 p.m.
> Also, if you have the knowledge, equipment (a
_good_ logic analyser, which
> is not the sort of thing most hobbyists have) and time, it may be worth
> grabbing waveforms arround irreplaceable custom chips when you first power
> up the machine This information may be very useful if you even need to
> recreate them. On the other hand, knowing what to record, and what to
> relate it to, is often non-obvious.
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.
If a custom logic chip has any sort of complex state machine (nearly all
do), simple probing will probably never reveal all of the states.
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.
And of course, grab hold of every spare chip available off of donor machines.
William Donzelli
william(a)ans.net