S - 100 64 KB Static RAM CompuPro/Godbout RAM 17 175C Hitachi HM6116 CMOS
Item History & Price
| Reference Number: Avaluer:51466224 | Vintage: Yes |
| Type: Memory | Brand: CompuPro/Godbout |
| Compatible Brand: S-100 | Custom Bundle: No |
| MPN: Does Not Apply | Modified Item: No |
When the Altair came out in 1975, your RAM options were bad and worse.
Static RAM was small, expensive, and hot. The fabs didn't know how to make CMOS at the time, so memory state was held in the current flow through a junction transistor.
Dynamic RAM could hold state on the charge of a FET gate so there was hardly any current flow, giving very low power dissipation. However, the charge did leak off the gates eventually, so refresh cycles were needed, adding complexity. My unders...tanding is that the big bugaboo with dynamic RAM at the time was noise, both on die and on the PCB. Even though it wasn't perfect, dynamic RAM came at a price were I could finally get up to 48 or 64 KB. Being able to run CP/M was worth the occasional flakiness of the dynamic memory of the day. I still reflexively save my work to disk due to habits developed in those days.
But when technology advanced far enough to get good yield on dense CMOS processes, we finally had the stability and simplicity of static RAM coupled with low power consumption. The Hitachi HM6116 chips ran completely cool, only needed a single 5V power supply, and were solid as a rock. I finally had enough memory to run CP/M and the reliability of a professional system.
This board also benefited from the work of Bill Godbout, George Morrow, and others on refining the S-100 bus spec into the definition of IEEE 696. That closed up a lot of the ambiguities that had previously led to trouble between boards from different vendors.
I used this board with my CPU-Z board also from CompuPro/Godbout and the two were a winning combination. That board is up on a parallel auction. One cool feature they both support is eight more address lines for banked RAM so you can take a system up to 16 MB in theory. You'd run out of S-100 bus slots long before that with just 64 KB per board.
This board supports an IMSAI front panel mode, even though that's not allowed by the IEEE 696 spec. My idea of computing was to punch reset and boot CP/M from disk, so a front panel never held much interest for me after CP/M arrived.
The included original Technical Manual has a date code of 1/82 and that seems consistent with the chip and PCB artwork date codes suggesting this board was built in early 1982.
The 16-page Technical Manual includes a technical overview, all the configuration instructions, schematic, parts list, and component layout.
Unlike my earlier RAM boards, there's not a rework wire or jumper wire in sight. This board uses the modern invention of the DIP switch to avoid jumpers.
I see no flux residue on the solder side, suggesting that I bought this board assembled.
It's in good shape, with just a little bit of dust on the horizontal surfaces from when it was operating. It's been kept closed up since then. I have to sell it as-is because I can't test it, but I have no reason to believe that it's not as good today as when I powered it off for the last time. I hope it brings you as much happiness it brought me all those years ago.
I will ship with USPS Priority Mail.
Static RAM was small, expensive, and hot. The fabs didn't know how to make CMOS at the time, so memory state was held in the current flow through a junction transistor.
Dynamic RAM could hold state on the charge of a FET gate so there was hardly any current flow, giving very low power dissipation. However, the charge did leak off the gates eventually, so refresh cycles were needed, adding complexity. My unders...tanding is that the big bugaboo with dynamic RAM at the time was noise, both on die and on the PCB. Even though it wasn't perfect, dynamic RAM came at a price were I could finally get up to 48 or 64 KB. Being able to run CP/M was worth the occasional flakiness of the dynamic memory of the day. I still reflexively save my work to disk due to habits developed in those days.
But when technology advanced far enough to get good yield on dense CMOS processes, we finally had the stability and simplicity of static RAM coupled with low power consumption. The Hitachi HM6116 chips ran completely cool, only needed a single 5V power supply, and were solid as a rock. I finally had enough memory to run CP/M and the reliability of a professional system.
This board also benefited from the work of Bill Godbout, George Morrow, and others on refining the S-100 bus spec into the definition of IEEE 696. That closed up a lot of the ambiguities that had previously led to trouble between boards from different vendors.
I used this board with my CPU-Z board also from CompuPro/Godbout and the two were a winning combination. That board is up on a parallel auction. One cool feature they both support is eight more address lines for banked RAM so you can take a system up to 16 MB in theory. You'd run out of S-100 bus slots long before that with just 64 KB per board.
This board supports an IMSAI front panel mode, even though that's not allowed by the IEEE 696 spec. My idea of computing was to punch reset and boot CP/M from disk, so a front panel never held much interest for me after CP/M arrived.
The included original Technical Manual has a date code of 1/82 and that seems consistent with the chip and PCB artwork date codes suggesting this board was built in early 1982.
The 16-page Technical Manual includes a technical overview, all the configuration instructions, schematic, parts list, and component layout.
Unlike my earlier RAM boards, there's not a rework wire or jumper wire in sight. This board uses the modern invention of the DIP switch to avoid jumpers.
I see no flux residue on the solder side, suggesting that I bought this board assembled.
It's in good shape, with just a little bit of dust on the horizontal surfaces from when it was operating. It's been kept closed up since then. I have to sell it as-is because I can't test it, but I have no reason to believe that it's not as good today as when I powered it off for the last time. I hope it brings you as much happiness it brought me all those years ago.
I will ship with USPS Priority Mail.
