I think a simple external RAM expansion connected to the right side port of the computer would be nice as well, without needing to solder and modify the original HW.
That's a perfectly reasonable desire, especially for collectors that don't wish to modify original hardware, but don't forget ... when Enterprise itself offered to expand 64KB machines to 128KB, they did it with an internal memory expansion that required opening the case.
From my own personal point of view, if I've got to open the case to upgrade the EXOS version from 2.0 anyway (presumably with a hardware mod and Zozosoft's EXOS 2.4), then I might as well install the extra RAM internally as well at the same time and then be left with a clean-looking machine.
Do we know what GAL Saint used? Pinouts are often pretty standard so Atmel's ATF16V8B might just be a drop in replacement.
According to both the photos that I've seen, and the GAL programming file that gflorez pointed out, Saint used a Lattice GAL16V8 (datasheet attached).
The photos show that he started with the 25ns part, and then used the 15ns part later on (probably just because that's what he could find to buy).
It looks like the GAL16V8 is both pin and electrically compatible with Atmel's ATF16V8B, so there *should* be no problem using the newer chip.
Alternatively if you were making a new board, I believe many circuit manufacturers will programme the GALs for you when get the board made up. (Although I don't know what that does to the cost and IMHO, there's nothing wrong with your 74HCT138 idea.)
Incidentally, the ATF16V8B is exactly the one that I used in my internal memory expansion. They're very easy to program using cheap universal programmers.
JLCPCB do actually offer an SMT version of the ATF16V8B, but honestly, both the Lattice and Atmel GALs have a 20 year rating for the programming, and I really don't like the idea of a new memory expansion board on a 35 year old computer having a built-in time limit that will eventually cause the board to fail.
The chips on Saint's design are both socketed, so at least the GAL can be easily re-programmed if it starts to go bad, but we lose that option if we use a SMT version of the ATF16V8B.
So, from my point of view, that either means choosing Saint's design with its socketed DIP chips, which means more expensive parts and more soldering ... or choosing to try to finish off the 74HCT138 surface-mount design and having the SMT chips mounted at the factory, which means using cheaper components and having less soldering to do when the boards are received.
As it is, I just received a new TL866II Universal Programmer to replace my very old and broken EPROM Programmer from the 1990s, and so I should now be able to program both the newer ATF16V8B chips, or the older GAL16V8 chips.
On the other hand, I think like Dr.OG: with the arrival of the SD cartridge you no more need to have something connected to the expansion port so, it is the obvious place to connect a Ram expansion if you fear to break the Enterprise while dismantling it completely....
I agree, and I'm not looking forward to taking my Enterprise apart, but I don't see much option if it still has EXOS 2.0 inside.
Then, as you say, there is the issue of the external solution needing an expensive edge connector, and also really needing to have a case for the board so that it is both physically supported and protected.
Also, there is a thing I don't understand: why ordering the PCB builder to solder the components? these jobs are not cheap, and misses you the enjoyment of soldering the PCB by yourself.
Hahahaha ... we're very different people. I'm afraid that I really don't enjoy soldering, and there is no way that I would I would even attempt to try to solder SMT components.
Yes, I *can* solder; I both played with electronics as a kid, and I did some electronics classes at university, but really I'm a software guy, and not a hardware guy.
As for the cost, it *looks* like JLCPCB will charge $20 USD for the setup, and then maybe $0.1 USD per board for the soldering ... which seems reasonable if someone orders 5 or 10 boards.
I don't know if there will be other charges, and I won't know that until I have created a board layout that I can upload to them and get a quote.
It is slow work since I've never done it before.
