A590 U5 Ram Controler

[ozkano]

one of mine A590's U5 ram controler PAL is missing, I want to program this chip, I tried to clone by using my GAL programmer but I cant get firmware, is there anyone has this firmware


 :-)

[fiat1100d]

Unfortunately the original PAL seems to be protected from read... You should buy another one, the "FIFI" chip found on the A2091 should do the same job, since I saw photos of newer A590s fitted with this chip: probably they first used PALs then made their custom IC with same function.

[Zac67]

U5 is always a 16L8A PAL. It's the RAM controller, so no memory expansion without it. Even getting the chip might get difficult, but you'll also need the code.

[ozkano]

without U5 A500 does not boot, is there any way to unlock PALs security

[Zac67]

Hmm - that's a shame. I don't think there's any way to fool read-protected PALs, otherwise the copy protection would be pretty useless...

At first glance I'd have thought that the A590 should start - maybe the RAM is accessed even in amnesia mode and the bus hangs due to missing ack. You can try bridging _RAMSEL to _DTACK (pin 5 to 18); not exactly nice, but it might bring at least SCSI to life.
(I always use a small resistor ~100 Ohms for bridging so nothing can smoke.)

[freqmax]

Isn't PAL chips just a large truthtable booleanly speaking?
Such that it should be possible to scan all combinations and work out the right formula with your mind & some time?

[Zac67]

Well, somewhat. Does this help?

[freqmax]

Feed the truth table into a file. Then setup such that you can  try an algorithm and verify it or get what's missing. Then it's all trial & clever thinking

[rkauer]

 I think the only solution is buying an already dead A2091 (not exactly a hard job) and sack the U5 from it, praying the chip is good.

 A "WTB" post on Amibay or here on the bazaar/trade section can bring the thing.