Hey all -
I've recently started to get back into my IIgs and that includes opening them up and re-aquainting myself with what's installed.
My ROM 3 GS has a RAM expansion from Sequential Systems, (c) 1991, one of the cards without the RAM-GS silkscreening. It's a 2MB card with the open row of sockets available for expansion.
I've checked the original documentation and there's no mention of what chips to use to bring the card up to the 4MB maximum. The existing, soldered on packages are hard to read and my google efforts haven't gotten me very far in trying to find anything beyond a datasheet for the Toshiba TC511001Z-12 packages that are in some of the locations. The chips all seem to be a hodgepodge of whatever was on the shelf when the cards were soldered together.
Does anyone here have any experience with these cards and know for sure what chips I should be looking for? I assume they're all obsolete by now and that it might be more economical to buy a used and fully-populated card instead, but that's no fun!
The Micron chips are MT401026Z-10, and the Toshiba chips ar TC511001Z-12. So according to the way they were binned, the Micron chips have a faster access time at 100 ns compared with the Toshibas' 120 ns. The timing is set by the computer, of course—chips binned differently like this can coexist.
Both have the same geometry, 1M x 1, and the same package/pinout: ZIP-19. You can search for these parametrically at Octopart.com or Findchips.com to find compatible chips from every manufacturer. Since they are so old I would guess they are out of production so you would be dealing with surplus chip vendors, which often means you have to submit a request to get a price quote.
Kind of what I was expecting, since digikey and similar don't have anything in a ZIP package available. I'll have a quick look around.
Thanks! Your eyes are much better than mine!