65C02 wrote on 2021-06-08, 22:38:
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The exact motherboard model is an Asus TX97-E, and the SDRAM I used came from a dell that just stopped working suddenly. Both are Samsung 256MB PC133. I was hoping to upgrade this garage sale PC to the maximum supported 256MB to make Windows 2000 run a little better. Now that you mention it, it would definitely make sense that to do so, I would need 2x128 rather than 1x256. I believe the memory has to be installed in pairs on this motherboard.
No , the Pentium has a 64b wide bus, so it needs memory in 64b blocks. If you're using 72p SIMMs that are 32b wide you need to install them in pairs. 168p DIMMs are however already 64b wide, so you can install them one at a time.
Now, the i430TX chipset can only cache 64MB, so unless you're actually using everything over that, it will actually perform worse, particularly in Win9x or DOS as they fill up the uncached RAM first (WinNT and derivatives do it the other way round, so far less impact). Officially it accepts max 256MB, with max 2 DIMMs with 16 8Mx8 64Mb chips each (note capitalization: 1B=8b). But... Intel was a bit conservative with their memory support in the late 1990s. Like the similarly-specced i440LX and EX, the i430TX chipset can actually handle 128Mb chips, allowing you to do 256MB per DIMM and 512MB total.
But...
Not many boards could handle it. Some just use the first 64Mb of each chip, others show more, but don't run stable. Now, it really would have helped if you'd given us more detailed information, in particular how many & what type (code written on them) of chips are on those DIMMs, and how much RAM the motherboard actually detects at POST.
There are three ways to get 256MB SDR-SDRAM DIMMS:
1) 16 chips of 128Mb (16Mx8) each. These might work at full capacity on your board.
2) 8 chips of 256Mb (32Mx8) each. These might work, but at best at 1/2 capacity, maybe 1/4.
3) 16 chips of 128Mb (32Mx4) each. Non-JEDEC. Won't POST in any Intel chipset system, and precious few others.
As your system POSTs, 3 is ruled out. 2 probably wouldn't give you problems (just less RAM), so I suspect this is 1.
That gives you three probable causes here, and one likely fix for two of them:
1) your board can't handle the 256MB DIMMs. You need to get smaller DIMMs with smaller chips, i.e. 128MB with 16 chips (64Mb each)
2) your board can handle the 256MB DIMMs separately, but gets unstable when the total size goes over 256MB.
3) your board isn't the problem, handles 512MB fine - but Win9x needs registry hacks to use 512MB and above.
Given you can install WinNT/2k, which are far heavier on the hardware, I don't think it's 1 or 2, which leaves 3. There's an extremely simple solution here: remove one of the DIMMs so you drop down to 256MB total.
*IF* my assumptions based on insufficient information are all correct, that will allow you to install Win9x successfully.
Once again, consider finding a simple 64MB DIMM and using that. It's highly unlikely any software that will run happily on a P166MMX will need that much, and with Win9x having all your ram cached matters.
P.s. if this is the case, and your board actually supports 512MB, could you post your BIOS version (visible in the POST-screen) here? We've had quite a few discussions about i430TX and 512MB. I know it's possible, this would be a clear example.
