Arcane RAM question
October 17, 2012 3:09 AM   Subscribe

Trying tp revive (as an educational exercise) a 17-year-old computer with an unusual memory structure.

Because of a RAM shortage at the time, the mfr put 4 SIMM (72p) slots and 1 DIMM (168p) slot, so the base memory could be either 2 SIMMs (which apparently must be in pairs) or 1 DIMM, depending on which was available at the time of manufacture. Processor is a 166mhz Pentium, and max RAM is 128mb, which would be 4x32mb if the SIMM slots are used. The DIMM slot was meant for either a 16mb or 32mb DIMM, but I wonder if a computer of this era could correctly interpret a 128mb DIMM? The SIMM slots top out at 32mb capacity, but no mention is made of the DIMM. Any way of knowing this without buying the part and plugging it in? IBM Aptiva 7661-c76, 5v 60ns np edo ecc unbuff RAM.
posted by ackptui to Computers & Internet (4 answers total)
You could get a bag full of free memory and try it out. There are other nuts like us with bags full of memory. I probably have a few sticks of everything that are wasting away now that I am not trying to resurrect old Aptivas and such. (...actually mostly Thinkpads.)

email me (in profile) and help clean out my lab. I'm down to two Thinkpads and they are maxed so the memory collection is kinda sorta not all that useful to me right now. your project is probably a better use that the one i had in mind (i.e., using them to reinforce concrete footings as a joke to future archaeologists.)

IMO, the best way to answer this question IS to try it out. at the age of this machine, getting reliable tech info on it might be challenging, and you'd need some specific hardware docs to see if the motherboard would function with larger memory sub-assemblies. it's quite possible to find that info, and with IBM probably more so. (I have found some really arcane tech dox for stuff you would not believe, but to do it, sometimes I have to put a project on hold for a few years. no kidding. patience usually pays off, but you have to keep looking.))
posted by FauxScot at 4:42 AM on October 17, 2012

A 168-pin EDO module might or might not work. Most 168-pin DIMM modules contain an SPD "serial presence detect" chip, which identifies configuration (including capacity). So the real problem isn't an electrical one, where I'd give you very good odds that the DIMM would be electrically compatible, but rather whether the board implements SPD, and if it does, whether the BIOS can understand the SPD on the DIMM. It is less-likely to understand it if there were no commonly available parts of the correct size at the time of the last BIOS update, and if it doesn't understand it, it will either not work at all, or see it as the wrong size, or be unstable. And that's kind of the fun of it all, because you never really know if it actually works because it should, or because it's just almost-working and at the bleeding edge because the timing's off or something like that.

Unfortunately, the best answer is really just to try. And, unfortunately, given that this is IBM, your chances of success are somewhat reduced, because IBM was really big into proprietary memory.
posted by jgreco at 4:51 AM on October 17, 2012

Given the age of the computer, the SIMM/DIMM slot numbers, the maximum memory numbers given and the fact that its an IBM I'm going to pin this down to the 430VX chipset. The 430VX chipset only supports 4Mx64 DIMMs at most on the DIMM slot which is a single 32MB DIMM.

If you can give us the actual chipset we can probably try to narrow it down further for you but that's my educated guess.
posted by Talez at 3:16 PM on October 17, 2012

I got the model number of the machine wrong in the original post, it is actually an Aptiva 2176-c67.
The chip on the board is a 437vx. I was able to determine which of the ram sticks was causing the memory error and took them out, which leaves me 2 x 32mb simms installed, and 2 simms and the dimm slots empty. For some reason now, I cannot boot from the cd drive. Went into the bios and disabled everything but the cd, and it put up a graphic on the screen of a floppy going into the floppy drive. Anyone have any ideas?
posted by ackptui at 11:18 AM on October 18, 2012

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