I've seen a GAL20V8B used in a Commodore 64 PLA project recently. The GAL20V8B is obsolete but still easy to get from Aliexpress and the Minipro programmer supports it.

I assume the biggest pitfalls on using it would be:

1) Being obsolete, not a good idea for high volume products (not an issue for me). Only for small one-off projects.

2) Coming from China, expect a high failure rate and/or fakes. However, they are so dirt cheap that may not matter.

I'm thinking of buying a few just for giggles but seems like they would be a nice fit for some small glue logic here and there (especially prototyping).

What are you thoughts on that one or other GAL's?

Thanks

_________________
Cat; the other white meat.

The ATF22V10 would seem to be the obvious choice, IF your programmer that has it on the list. I think it's only the V2 minipro that does.

I used 1 x 22V10 in Ruby6502 and 2 in Ruby816.

Description of the 6502 board: https://projects.drogon.net/6502-ruby/

Picture of the '816 board:



I buy Lattice parts from China - they're all board pulls that have (probably) been programmed just once (from what I can tell anyway). I've not had any issues - they're all worked for me, but it's possible I got lucky. I use a Genius G540 programmer off a WinXP Laptop, but I use something called GALasm running under Linux to generate the JED files.

I did buy a Minipro programmer, but (a) an early one and (b) turned out to be a "clone" and it won't program them. I'm told the next (current) version will program them and the still in-production Atmel (Microchip) ATL22V10 versions - I bought some of them new, but neither my old programmer nor the G540 will program them. (Currently I'm loath to buy another programmer, but I may in future)

If you can program them, then unless you want to be totally authentic to some historical design then spend the money and run! There is a fine-line between the purist retro and something a little newer though, but we had one time (mask) programmable logic chips in the late 70's/early 80's (ULAs) and user-programmable PALs in the early 80's too, so for me, it's retro enough, and is saving me 3-4 TTL chips and they enabled me to get my boards running code more or less immediately.

-Gordon
(edit to add photo+link)

_________________
--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

At one time, I had considered using a GAL in one of my designs. However, small CPLDs, such as the Microchip (Atmel) ATF1504AS, take up little more physical space than the largest GALs, despite offering more logic resources and more I/O pins (32 on the 1504AS in a PLCC-44 package). Also, most CPLDs can be programmed in-circuit via JTAG, conferring even more flexibility.

At this time, I just don't see anything in favor of using a GAL instead of a small CPLD.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

I used an ATF22V10CQZ in my recent C02 Pocket SBC for a single glue logic chip. It provides selects for EEPROM and RAM, 5-I/O selects that are 32-bytes wide and PH2 qualified memory read and write lines. This was my first ever use of single glue logic, and I'm very happy with it. I have a Dataman 40Pro programmer which supports the Atmel devices, so erasing, programming and verifying is trivial.

_________________
Regards, KM
https://github.com/floobydust

There's also the ATF750 series, which uses a 22V10 form factor and pinout but has more internal resources. Potentially useful if a 22V10 has enough pins but the logic doesn't quite fit.

Early on in the design of POC V2, I looked at the ATF750 and then the ATF2500. They are both oversized GALs and, I think, more difficult to use than a CPLD. I never got past the consideration stage with them.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Actually, I have some of the ATF750CL CPLDs as well. I also had them working in the C02 Pocket SBC in place of the ATF22V10. The main reason I opted for the ATF22V10 was it had a lower current consumption in the actual circuit. Needless to say, my requirements for logic were easily handled (with the 22V10) so the 750 wasn't necessary. To be honest, I don't consider myself skilled enough to determine when I would use the ATF750 over the ATF22V10, which likely means I haven't had a requirement for anything that complex yet... maybe time will tell, we'll see.

My current hardware project is an I/O adapter for the C02 Pocket SBC. I'm using an ATF16V8 for glue logic and am working around WinCUPL and odd results to get it working as I need it... once again, my familiarity with WinCUPL and the programmable logic chips is biting me a bit, but I'm still pushing it (and myself) along.

_________________
Regards, KM
https://github.com/floobydust

The main feature of the ATF750 series is that it has a set of internal register bits and associated minterm products which are *not* associated with an external pin output, but can be fed back into the minterm product banks like the real pins. In effect, the chip can store and use 20 bits of state instead of the 10 bits of a 22V10.

Probably a lot of valid 22V10 uses don't use the state storage capability at all, let alone requiring twice as much of it. But at university, an extra-credit assignment I did could have been done with a single ATF750, but required two 22V10s, precisely because of the shortage of internal resources; I had enough pins to drive everything I needed, but not enough to do that *and* store the underlying state machine.

I love GALs. Whether new or old. For the most part I buy Lattice pulls and have never had a bad one, even though they come from China.

Mostly employed in typical glue logic. If you get the 7ns ones they offer such a huge improvement in space and speed over using traditional logic. But there are other advantages too, like providing flexibility and simplicity in circuit layout as well as the ability to update or alter functionality without a soldering iron.

I've used them in 7 of my last 10 projects.

So far I've not required anything larger than the 22V10, but I've used 16V8s and 20V8s as well.

_________________
Bill

Just watched this little video:

https://www.youtube.com/watch?v=GKyoh_gGTYM

It talks about replacing the custom PLA with 2 x GALs in the C64...

-Gordon

_________________
--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

Yep, and one of the GALs he had was defective.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Rochester Electronics sells a few varieties of GALs, but they have (roughly) a $250 minimum order. I confess I've toyed with the idea of plunking down for 50 or so GAL26CV12s: https://www.rocelec.com/part/latlatgal26cv12c-15lp

Do you have a programmer that can work with the 26CV12?

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

I have a GALBlast kicking around somewhere in the basement.