18 Nov
2005
18 Nov
'05
8:23 p.m.
Date: Thu, 17 Nov 2005 23:33:45 +0000 (GMT)
From: ard at p850ug1.demon.co.uk (Tony Duell)
Some manufactuerers did not copy-protect their PALs.
For example, all the
PALs in the VAX 11/730 CPU are readable (for all they're the key to the
design). All PALs in every PERQ I've seen (including the AGW3300) are
readable. All PALs in the Torch XXX -- apart from those on the (3rd
party?) 68020 kludgeboard -- are readable. But then again, most PALs on
clone ISA boards are protected.
If the original chip is a HAL, you are out of luck. HAL == Hard Array
Logic, it's a mask-programmed equivalent to a PAL. I've never found one
that can be read out, I suspect the circuitry simply isn't there.
There are a couple of articles in the archives about reverse
engineering the behaviour of PALs. One article started out very
promisingly (to my inexperienced eye) and the author stated that
parts 2 & 3 were to follow, but they never did. Oh well.
I would like to clone the external floppy drive and SCSI adapter for
the Outbound Model 125. I've acquired most of the required parts
for each. However, they each have a GAL 16V8 (just one per product)
installed. The terror at trying to figure the contents of that GAL
has been stalling me for months (well that, plus all the other stuff
around here, like getting the autumn garden planted).
How heat sensitive are PALs and GALs? Am I likely to deprogram the
thing when I desolder it from the board?
Jeff Walther