WTD: S100 Static RAM card

Brent Hilpert hilpert at cs.ubc.ca
Fri Mar 27 17:04:27 CDT 2015

On 2015-Mar-26, at 1:34 PM, Philip Lord wrote:

> Hi all,
> I’ve been struggling getting a 64k Dynamic RAM card back up and working in my IMSAI 8080. In fact I’m giving up on the DRAM card in this system and have decided to start looking for a SRAM card that can get the IMSAI up to 56k.
> In terms if SRAM cards, I presently have:
> 2 x Problem solver RAM16 cards - both seem to be working.
> 2 x 8K RAM cards - both seem to be working.
> Less cards generating heat, and putting stress on the old power supply is obviously best, so I’d be looking for either:
> - 1 x 16k SRAM card (for a total of 4 RAM cards (3 x 16k + 1 x 8k) in my system). A PSS RAM16 would be preferred for sake of consistency, but obviously not crucial.
> - 1 x 32k SRAM card (for a total of 3 RAM cards (1 x 32k, 1 x 16k + 1 x 8k) in my system)
> - 1 x 64k SRAM card that can have the last 8k bank turned off
> I would love to hear from anyone with one of the above cards who would be willing to pass it on.

If you're trying to remain period, the 4K / 8K / 16K boards would be more coincident with the IMSAI. What you have there sounds like a pretty typical growth line for a hobbyist S100 unit for the time - adding memory boards as finances allowed. Besides, near-empty S100 crates look rather sad - the more boards the better! AIR, the Altair power supply was a little anemic for the its slot-count capability, but that was something the IMSAI rectified or improved upon.

Presuming the remaining 8K address space you have there is ROM, a board(s) with phantom capability may be what you want, to allow 64K RAM.

64K boards are kind of cheating for an early S100 machine, unless you want to do something with bankswitching and multiple 64Ks.

ebay prices for routine S100 boards do seem excessive - 100+$/board (triple or more if it's a MITS board), should be half that, IMHO.

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