Macintosh Classic CAS PAL / ROM Replicas

[robin-fo]

Hi everybody

I'm currently assembling a Classic Reloaded board from @Kai Robinson (bought from @MacEffects ).
On my donor board, the ROM and CAS PAL chips lost some legs due to the battery explosion.
Is there a possibility to replicate the CAS PAL chip using something like a ATF22V10C?

I have a TL866 programmer...

 

[max1zzz]

As far as I am aware no one has yet cracked that PAL so it's a salvage it form another board part unfortunately
Maybe @Bolle can use his expertise to recreate it?

 

[jajan547]

I actually have some Plus ROMs premade if need be.

 

[retr01]

Now I know who to bug, @jajan547, for the older compact Mac ROMs!

 

[robin-fo]

I actually have some Plus ROMs premade if need be.

What about Classic ROMs?

 

[max1zzz]

What about Classic ROMs?

Classics need a 27C400 which you need a adapter to be able to program in most modern programmers, if you get stuck let me know as I have the chips and programmer to make them if needed

Actually thinking about it I might have a spare CAS PAL too.... If no one else jumps in I'll have a look through the scrap board pile tomorrow

 

[jajan547]

I can do classic ones too

 

[retrotechtive]

I am now also in need of a CAS PAL IC for my Macintosh Classic, to replace a dead one.

Any progress on this that anyone knows about? @Bolle I saw you mentioned above - are you able to assist on this?

Thanks (also, this is my first ever post on this forum so... hello all )

 

[robin-fo]

As my Macintosh Classic restoring project has stalled, I didn't do any reverse-engineering attempts yet..

 

[retrotechtive]

As my Macintosh Classic restoring project has stalled, I didn't do any reverse-engineering attempts yet..

Thanks for the quick reply - that's a shame, I don't think mine's in any state to get information from I have removed it from the board, and it doesn't seem to even register with my programmer. I didn't expect it to read, but perhaps at least show itself as present if it's working at all.

Did you manage to find any schematics for the IC itself? Maybe someone (or even myself with a bit of a ramp up of knowledge first) could recreate one from the original logic/equations..?

 

[Bolle]

and it doesn't seem to even register with my programmer.

Depending on your programmer that's normal behavior for PALs. On most of them there's no signature or anything to read for the programmer to identify the chip. Even worse programming algorithms vastly differ between manufacturers and even different PAL revisions from the same manufacturer.
There's a good chance that trying to read a chip with an incorrect chip type selected will result in a damaged PAL.

From looking at the schematics pin 27 seems to be one of the CAS outputs so the PAL has to be some weird type... PAL20L10 or a 22V10.
I have a spare chip right here, going to put it into the queue for things to look at. From looking at the schematics it can't be too complicated if there's no sneaky feedback timing hacks involved...

 

[retrotechtive]

@Bolle, you are my new hero

I had guessed it was most likely a PAL22V10 (didn't consider a PAL20L10 though), and had tried to use the programmer (a TL866-II with the adapter for PLCC-28 ICs) to detect the pins, but it failed to detect any of them at all. I admit I did play around with types after that, so even if it was working before (which it didn't seem to be when running the board), it probably won't be now from what you said.

I don't currently have any GALs myself in this package type, can you confirm which ones would be good for this? I was looking to try one of these more modern ones: a ATF22V10CQ-15JU. Would that work (whether I connect the extra power and GND pins or not), or should I be looking for an older GAL22V10 instead? Obviously, I have no JED files for this yet, and am fine to wait for an expert like yourself to get around to making some, though I may try blundering about myself deriving something from the older Mac Plus ones to see if I can come up with something compatible (but I'm a total ignoramus on this type of work at the moment so I'm not expecting a fast breakthrough )

 

[Chartreuse]

I don't currently have any GALs myself in this package type, can you confirm which ones would be good for this? I was looking to try one of these more modern ones: a ATF22V10CQ-15JU. Would that work (whether I connect the extra power and GND pins or not), or should I be looking for an older GAL22V10 instead?

The Atmel ATF22V10 and Lattice GAL22V10's are interchangable in use and the same JED file will work on either with no issues. The only difference really is how to program them. The Atmel chips use a completely different programming algorithm. Though the rather cheap TL866II (not the original TL866A/CS, that can only do Lattice ones and has a broken 22V10 programming code) can program either just fine.