What happens when you disconnect the hard drive? Does the bootup complete?

Meatball wrote on 2022-01-30, 18:42:

What happens when you disconnect the hard drive? Does the bootup complete?

Nope! Tried it just now and even without the hard drive connected it still restarts itself upon reading the floppy disk.

I think you might have a bad simm or something is unstable at your current clock speed.

Try removing 4 or 6 simms and see if the issue goes away.

Also see if you can jumper your motherboard to run at a slower speed and make sure your ISA bus is running at 8mhz in the bios.

If that doesn’t fix it, try swapping put cards to see if you have a failing add-in board.

SLC2 chip? What CPU is that, exactly? And did you set the BIOS properly for it, this looks to me like you've have it set to FLUSH and the input is not connected or even supported by the chipset. So each DMA will cause cache and RAM to desync, a bad thing to have in a computer system. Try BARB setting, or if there is no such option, disable CPU internal cache in BIOS - if either helps, you know you can't use FLUSH for cache coherency. Pity but not uncommon on many mobos.

douglar wrote on 2022-01-30, 20:24:

I think you might have a bad simm or something is unstable at your current clock speed. […]
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I think you might have a bad simm or something is unstable at your current clock speed.

Try removing 4 or 6 simms and see if the issue goes away.

Also see if you can jumper your motherboard to run at a slower speed and make sure your ISA bus is running at 8mhz in the bios.

If that doesn’t fix it, try swapping put cards to see if you have a failing add-in board.

I only have 2 RAM SIMMs but I'll check the BIOS to see if some default setting (I don't have a CMOS battery right now) is set incorrectly. For some absurd reason this BIOS defaults to not even having floppy seek enabled...

Looking at my BIOS settings, I don't see anything about BARB or FLUSH and since this CPU is soldered to the board and has a heat sink glued on, I don't even know what speed it's running at to adjust the ISA bus speed.

EvieSigma wrote on 2022-01-30, 23:17:

Looking at my BIOS settings, I don't see anything about BARB or FLUSH and since this CPU is soldered to the board and has a heat sink glued on, I don't even know what speed it's running at to adjust the ISA bus speed.

Oh, if that's a mobo with actual IBM chip on it then please do not try to remove that heatsink. You will rip the CPU off the mobo, and damage the pads, before that glue lets go. I bought a mobo with such damage for parts, pity, it looked nice and was a rare case of SX-class chip with cache, but since it's IBM it has different control lines to Cyrix CPUs.

Anyway, do try to test with "Internal cache" set to disabled. Although with soldered CPU the mobo should correctly handle the DMAs, but it can be damaged somehow. Also your DRAM and cache settings might be too optimistic, try 1WS on cache and DRAM R/W. That's before or after you test with cache disabled of course, no point in setting waitstates for disabled cache. If that helps then try to lower those WS to zero, one at a time, and re-test.

Deunan has good suggestions.

AT clock selection would determine the divisor for the ISA bus.

What motherboard / cpu do you have?

douglar wrote on 2022-01-31, 01:44:

Deunan has good suggestions.

AT clock selection would determine the divisor for the ISA bus.

What motherboard / cpu do you have?

That is a good question, I don't actually know! I cannot find a clear manufacturer name or model number on the motherboard anywhere, and with the CPU heatsink being quite securely stuck on, the only way I can figure out the CPU is getting booted into DOS and running a program like HWiNFO.

Can you see a bios version string during boot?

I can, but I certainly can't understand it.

...6328...
->Alaris

So it is the ALARIS LEOPARD mobo. Chipset matches, CPU is IBM SLC2, also matches. That chip would be either 50 or 66MHz (clock-doubled) with 25 or 33MHz bus. I've never seen a 40MHz version, though I suppose it might just work with overclock, but I doubt it. In any case the CLK2/8 is perfect for a 66MHz, and if there is a /10 divider strap that would be ideal for 80MHz. And even if it was 80, with /8 divider it makes ISA clock 10MHz, most cards will tolerate that.

If ISA clock was somehow an issue with FDC I would expect it to throw read errors (bad data or CRC), not just glitch and reset every time. So I say it's cache related or perhaps DRAM being too slow for 0WS, I mentioned that above.

First off replace the dead CMOS battery...

Battery sounds like a good thing to do. Mkarcher found a thing in some BIOSes where if the battery status is low then they will always report the floppy drive to DOS as a 360k 5.25", no matter what gets set in the CMOS settings: Re: Strange Floppy Disk behaviour 486 . So maybe DOS gets part way through booting (the BIOS can get started using the floppy drive settings you set), then DOS asks the BIOS for floppy drive types attached, gets told the drive it's booting from is a 360k drive, and then can't read from the disk.

snufkin wrote on 2022-01-31, 11:01:

Battery sounds like a good thing to do. Mkarcher found a thing in some BIOSes where if the battery status is low then they will always report the floppy drive to DOS as a 360k 5.25", no matter what gets set in the CMOS settings: Re: Strange Floppy Disk behaviour 486 . So maybe DOS gets part way through booting (the BIOS can get started using the floppy drive settings you set), then DOS asks the BIOS for floppy drive types attached, gets told the drive it's booting from is a 360k drive, and then can't read from the disk.

I had never heard of that issue but it's a possibility. I'll have to get one of those adapters that lets you mount a CR2032 holder to the solder points for a barrel battery, I don't think this board has an external battery header.

EvieSigma wrote on 2022-01-31, 18:06:

I had never heard of that issue but it's a possibility. I'll have to get one of those adapters that lets you mount a CR2032 holder to the solder points for a barrel battery, I don't think this board has an external battery header.

Oh, it was definitely a weird one. Depending on your board revision, it looks like the Alaris Leopard has an external connector the other side of the AT Keyboard connector from the on board battery. Any board photos?

Deunan wrote on 2022-01-31, 00:26:

EvieSigma wrote on 2022-01-30, 23:17:

Looking at my BIOS settings, I don't see anything about BARB or FLUSH and since this CPU is soldered to the board and has a heat sink glued on, I don't even know what speed it's running at to adjust the ISA bus speed.

Oh, if that's a mobo with actual IBM chip on it then please do not try to remove that heatsink. You will rip the CPU off the mobo, and damage the pads, before that glue lets go. I bought a mobo with such damage for parts, pity, it looked nice and was a rare case of SX-class chip with cache, but since it's IBM it has different control lines to Cyrix CPUs.

Anyway, do try to test with "Internal cache" set to disabled. Although with soldered CPU the mobo should correctly handle the DMAs, but it can be damaged somehow. Also your DRAM and cache settings might be too optimistic, try 1WS on cache and DRAM R/W. That's before or after you test with cache disabled of course, no point in setting waitstates for disabled cache. If that helps then try to lower those WS to zero, one at a time, and re-test.

So I tried setting cache and DRAM to 1WS and that did nothing to solve the problem, and the same goes for disabling internal cache. So maybe it's a battery thing?

EvieSigma wrote on 2022-01-31, 23:56:

So I tried setting cache and DRAM to 1WS and that did nothing to solve the problem, and the same goes for disabling internal cache. So maybe it's a battery thing?

Welp, so much for easy fixes. You can also try disabling the hidden refresh, and then see if you can add even more WS to the '206 chip access, and the DMAs (especially the 8-bit one). These are the options on the right side of the advanced section. This is to see if there's maybe some sort of conflict between FDC DMA and RAM refresh (which would corrupt the RAM and cause hangs or reboots). If that doesn't help, and neither does the battery, then I'd assume some mobo damage. Inspect it, especially the area around battery since that's where corrosion would start.

Can you buy CR2032 holders that plug into the external battery header on a motherboard or do you have to build one? I know I've seen some people on YouTube using them.