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Author Topic: Internal memory expansion (Read 142455 times)

Offline dangerman

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Re: Internal memory expansion
« Reply #240 on: 2020.August.10. 11:18:12 »
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.

Sadly, the problem with an external RAM expansion (and why I decided to build an internal one as well) is that you need some kind of bus board or pass-through to connect an EXDOS as well. Maybe it doesn't matter if you have the cartridge SD card reader, but I can see why some people would prefer to solder something internally instead.


Offline dangerman

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Re: Internal memory expansion
« Reply #241 on: 2020.August.10. 11:41:08 »
Don't follow this if you later want to add some FlashRom to your expansion.

Good point about the FlashRom - that wouldn't work with my home-made expansions!  I guess it all depends how easy you want the routing on your memory expansion to be ;-)

Other 5V GALs, such as Atmel's ATF16V8B, are still widely available and affordable, but then that would be a change in Saint's design, and I don't know if that would work.

Then, whichever GAL is used, someone has to have the right equipment, and then take the time, to program it.

Do we know what GAL Saint used? Pinouts are often pretty standard so Atmel's ATF16V8B might just be a drop in replacement.

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.

Online gflorez

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Re: Internal memory expansion
« Reply #242 on: 2020.August.10. 12:06:13 »
Thanks Elmer for putting me near Saint or Kotek.... My only merit on all these years has been to take risks with my Enterprise to learn more in return. My first EP can be the proof that they build them very strong. Almost all the things I have achieved where by means of knocking and knocking my head against the information available. Thanks, Zozo, Geco, Pear, LGB, IstvanV, and others for being so patient with my constant questions....

Also, sorry, I don't want you to think that I am misprising your design. Only that my message was long, and yesterday was too late to continue writing.

But looking forward, your approach is neat and wonderful in its simplicity, enough to run SymbOS or other old or modern programs with very few components.

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....

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.

A last thing: EDGE connectors are expensive if not bought in China, so you must consider the overprice against the easiness to connect it. And, even if you have the Edge connector, it always need some trimming. I can aid you, as I have some experience on that.

Ok...., I offer my aid,  daring and interest on all that my limited skills will allow. .

Online gflorez

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Re: Internal memory expansion
« Reply #243 on: 2020.August.10. 12:17:18 »
About programmable chips. Don't think that is difficult to manage them, the only problem they have is obsolescence. Lattice's GAL are obsolete now, and also the substitutes.

But you can find the way to program them reading a lot of web pages... I and others have already done that, so you don't need to take that path. I have now a collection of programmers, some very old and others new, all very cheap. The usual problem is with the software that controls them, but you always can use Google to find it.

Offline elmer

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Re: Internal memory expansion
« Reply #244 on: 2020.August.12. 05:49:55 »
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. :(
« Last Edit: 2020.August.12. 05:53:45 by elmer »

Offline dangerman

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Re: Internal memory expansion
« Reply #245 on: 2020.August.13. 22:12:30 »
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.

Yes, I'd forgotten about the time limit. That would be very annoying indeed. You make a good case for using standard parts.

Online gflorez

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Re: Internal memory expansion
« Reply #246 on: 2020.August.14. 00:14:39 »
Which other time limits could exist on other components and we can't even predict them.....

We shouldn't live with that fear, every problem will be fixed in strict order of happening....

Do you think that the humble Enterprise was made to endure 35 years of use(...or more I hope)?

Offline emptiness

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Re: Internal memory expansion
« Reply #247 on: 2020.August.16. 23:01:09 »

I have absolutely no interest in "reinventing the wheel", nor do I believe that I have the knowledge, experience or skills to somehow invent the "best" internal RAM expansion.

I just want/need an internal RAM expansion for my Enterprise 64, and none seems to be currently available anywhere for me to buy, so I am trying to come up with an *easy* solution that requires minimal soldering or programming, that might be easy and cheap to order, and that hardware-novices could re-order themselves in the future.

Same here. I'd be happy to buy a couple of boards from someone or failing that solder a board if there's a design that I'm capable of assembling.

elmer, you're way ahead of me, if you do finalise a design and get as far as fabricating some boards please let me know. I'm happy to chip and in help with costs.

Offline elmer

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Re: Internal memory expansion
« Reply #248 on: 2020.August.19. 20:27:41 »
Which other time limits could exist on other components and we can't even predict them.....

We shouldn't live with that fear, every problem will be fixed in strict order of happening....

Do you think that the humble Enterprise was made to endure 35 years of use(...or more I hope)?

I agree, there's no point in worrying if something may break over time ... everything does eventually!

I see nothing wrong with using a GAL, I would just want it to be easy to reprogram if it starts to lose its flash-memory.

IMHO, that means that using a DIP-format GAL would be more sensible than using a SMT-format GAL, that's all that I'm saying.


elmer, you're way ahead of me, if you do finalise a design and get as far as fabricating some boards please let me know. I'm happy to chip and in help with costs.

I've had some help from a friend, and I'm (slowly) getting closer to having a simple board layout that could work.

Even if I can get a design where JLCPCB integrates all the SMT components, there will still be the EXP1 and EXP2 connectors that will need to be soldered on, plus the soldering on the Enterprise motherboard for the EXP1 connector and the EXP2 cable.

All of those should be low-tech 0.1" soldering that old folks like me are still capable of handling. ;)

Offline elmer

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Re: Internal memory expansion
« Reply #249 on: 2020.August.19. 21:55:12 »
Now 3 different wiring exist... little crazy :evil:




Universal cable which can be used with both Saint and Kotek type boards:



Urrrrggghhh ... that's annoying! :(

Are there actually any people using Saint or Kotek wiring that would even be interested if there was a new 512KB memory board available?

The reason that I ask is that the "original" wiring is probably the one that makes the most sense to me for a new board. The reason for that is because it allows for a simple 90 degree fold in the cable, just the way that the original Enterprise memory board cables were folded.
« Last Edit: 2020.August.20. 16:49:46 by elmer »

Offline geco

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Re: Internal memory expansion
« Reply #250 on: 2020.August.19. 23:16:00 »
Sorry if i misunderstood your post. I use probably Saint's 1MB board ( i did not open my ep), but if there is a new board also, i am interested.

Offline elmer

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Re: Internal memory expansion
« Reply #251 on: 2020.August.20. 21:58:01 »
If I didn't make myself clear before, this picture shows how the EXP2 cable was folded on the original Enterprise memory expansion board, which causes the different order of pins on the 1x10 connector in comparison to how Saint ran his cable.




Sorry if i misunderstood your post. I use probably Saint's 1MB board ( i did not open my ep), but if there is a new board also, i am interested.

I suspect that I wasn't clear in what I was asking.

I am trying to decide whether to use Saint's pin ordering of the EXP2 cable, or to use the original Enterprise pin ordering.

If folks (like you) who are already using Saint's boards are actually interested in having yet-another memory expansion board, even though it only has 512KB, then I should probably just use Saint's pin ordering so that people can keep on using the cable that they've already wired onto their motherboard.

Offline Judge

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Re: Internal memory expansion
« Reply #252 on: 2020.August.20. 22:53:10 »
I suspect that I wasn't clear in what I was asking.
I am trying to decide whether to use Saint's pin ordering of the EXP2 cable, or to use the original Enterprise pin ordering.
If folks (like you) who are already using Saint's boards are actually interested in having yet-another memory expansion board, even though it only has 512KB, then I should probably just use Saint's pin ordering so that people can keep on using the cable that they've already wired onto their motherboard.

I don't think it matters. You can connect this cable to all memory cards.

25306-0

25308-1

25310-2

25312-3

25315-4

The Kotek is missing two GND. This is the difference ...
« Last Edit: 2020.August.21. 13:50:06 by Judge »
Üdv.Judge

Offline Tutus

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Re: Internal memory expansion
« Reply #253 on: 2020.August.21. 09:24:22 »
Exactly. I don't understand what the problem is. You can design a card based on the documentation. Ok, it's already sold out and all the makers are gone. But it can be solved!

Offline Allf

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Re: Internal memory expansion
« Reply #254 on: 2020.August.21. 14:52:52 »
I assume the 2x5-pin connector on the original German description on the link (64k-Static-Internal.pdf) is annoying for elmer. Topic link
« Last Edit: 2020.August.21. 15:00:37 by Allf »