exxos's Atari, Amiga & retro forum

Looking for 4x 4MB SIMM memory for a stock TT-RAM card. If anyone can help me out, cheers!

Steve wrote: 26 Feb 2025 20:31 Looking for 4x 4MB SIMM memory for a stock TT-RAM card. If anyone can help me out, cheers!

I have a big bag of untested SIMMs I can have a dig through. I don't think I've ever seen a 4MB 30 pinner, though!

BW

@Steve. I think the other bag is mostly 72 pinners.

Any of these any good?

BW

I don't think they look compatible according to my research:

For the Atari TT RAM board you can only use the 1MB SIMMS with 8 chips,
NOT 9, 3, and or use the 4MB SIMMS with 8 chips.

If this quote is correct, no matter if I'm looking for 1mb simms or 4mb simms, they both need to be 8 chips types. Hmm I wonder if @stephen_usher knows is this is correct? Cheers

Sounds like you need non parity 4MB SIMMs.

I may have some 80-120ns, but very unlikely to have 70ns if thats whats needed. (IIRC that was very fast RAM for back then). And they will likely not be the 'burst nibble' mode ones either.

I think I just used some 4MB SIMMs from an Apple Mac SE/30.

If you have the other types there's no harm in trying. If they work then they work. :-)

Ok Stephen.

I will fish them out later tonight Steve. IIRC the Atari TT 'burst nibble' mode is FP or EDO RAM in PC terminology. I will see what I have.

Thanks all :)

You can always make your own: https://www.pcbway.com/project/sharepro ... 5f4da.html

Remember to buy 1,2mm PCB to make SIMM!

Then buy single side 72pins 16Mb 8 or 9 chips (toss the 9th chip for parity check) or double sided 72pins 32Mb (8 or 9 chips per side).

Make sure they are 4,194,304-word x 4-bit Dynamic RAM and not 1-bit

Like:
TC5117400CSJ
TC5117400BSJ
K4F160411D-B
KM44C4100CK
M5M417400CJ
MCM517400CJ
TMS417400ADJ

EDO should also work if you do the mod but not tested on Atari. Well, nothing above is tested on Atari as far as I know.

Well, this is what I have 30-pin SIMM wise. Most of it is 9 IC (parity stuff), but theres one non parity and even some 70ns modules in there if they will work.

My eyesight isnt what it used to be, so Im not sure what stuff is 0.5/1/4mb. it would be a great help if you can make out the SIMM details/markings from the photos! :)

So first, an overview: (N.B: the leftmost set are the only 8 IC ones I have and the 2nd from the left set is the only ones I know for certain work and are 4Mb (but 9 chip)
Then the above photo in closeups from L>R top to bottom:
And then I have a 30>72-pin SIMM converter/adapter with 8 of these on:
Ive got a feeling I sold (at least) 2 TT RAM boards and populated them with SIMMs, so its a bit less than I remember having.

Let me know if you think any of the above is worth a try.