andromeda wrote on 2021-03-31, 12:11:
I tested with 32MB double-sided strips, 8 chips on each side, the brands that work in my motherboard are goldstar and texas instrument,
the others that do not work are from the NEC, LGS, MT, I 've not tested 16MB strips, except one, no name which does not work,
OK, but what's the actual chip code on the chips on these modules?
For LGS it might be something like: GM71C17400BT6 Or maybe GM71C17403BT6.
See, particularly the comments that Goldstar chips do work but LGS (=Lucky Goldstar) don't suggests the problem isn't with brand but with age (Goldstar changed their name very early on in the 72p SIMM era), and that makes me suspect that even though the motherboard chipset is supposed to support EDO, this motherboard might not do so (or might need some BIOS tweaks). That 0 or 3 above is the difference between FP and EDO. If you post the chip code for each of the SIMMs that do work and those of the SIMMs that don't, we could see soon enough what the common factors are.
I have no other machine to test them, at the beginning the strips worked under dos, I had 72MB (2x32Mo + 2x4Mo), as soon as i in […]
I have no other machine to test them, at the beginning the strips worked under dos, I had 72MB (2x32Mo + 2x4Mo), as soon as i installed win95 it never worked, only crashes under win95,
and it corrupted the disk with weird characters, i had to repartition and reformat each time.
there, it no longer works at all, black screen.
now i have 2x8Mo + 2x4Mo (24Mo), it work fine.
I would have to test with a 16Mo texas instrument strip, if it works, it would mean that the maximum ram is 64Mo if not , the maximum ram is 32Mo.
You're changing far too many things at once. Test with *one* SIMM and see if that works. Then replace it with *one* other SIMM. Only after you're sure that both work separately, try to see if they work together. Take it one step at a time, then you know exactly which bit went wrong if it does fail.
What's suspicious here is that 72MB >64MB. This might be a cache / tag configuration issue. If so, a single 32MB SIMM would work fine. DOS hardly uses anything over 1MB, so no surprise that that wasn't affected like Win95.
There's one more option: memory bus loading. If you have the memory bus at full capacity, with at least 48 chips on it with that 72MB config, it might need looser timings than with less chips. Here again, one, two or three SIMMs likely wouldn't have problem.
So, go at it in a structured way to see if it's:
1) related to specific chip specs (i.e. doesn't like EDO, even one single SIMM of a certain type won't work)
2) related to total RAM size (i.e. single 32MB SIMM is fine but at some point it borks, most likely when you go over 64MB)
3) related to bus loading, so number of RAM chips regardless of size