98 is a picky bitch and can do this with any hardware changes, that said are you sure the CPU is working ? you may have a bad CPU.

Did you load BIOS defaults ?
Check to make sure you are on the latest version of the BIOS ?
Check the Dip Switches to make sure they are set correctly for the 1Ghz CPU ?

You may have to do a Fresh install of 98 to see if that fixes it ..98 never did like hardware being swapped around.

TrashPanda wrote on 2023-03-07, 13:58:

98 is a picky bitch and can do this with any hardware changes, that said are you sure the CPU is working ? you may have a bad CP […]
Show full quote

98 is a picky bitch and can do this with any hardware changes, that said are you sure the CPU is working ? you may have a bad CPU.

Did you load BIOS defaults ?
Check to make sure you are on the latest version of the BIOS ?
Check the Dip Switches to make sure they are set correctly for the 1Ghz CPU ?

You may have to do a Fresh install of 98 to see if that fixes it ..98 never did like hardware being swapped around.

The motherboard has "dipswitchless mode" which means I can set up everything in the BIOS. The BIOS also auto detects and configures everything correctly as far as I can see. It's a pretty darn good motherboard to be honest - it was the main reason I bought the PC.

For BIOS update: I prefer NOT to update an old BIOS unless I've ruled out everything else. According to the manual and other sites, the BIOS does not need an update to accept the CPU - the BIOS itself is from late 2000 so the 1Ghz CPU was already released by then.

I wonder if there isn't a tool that lets me test the CPU without having to spend several hours reinstalling Windows 98.

red_avatar wrote on 2023-03-07, 14:25:

The motherboard has "dipswitchless mode" which means I can set up everything in the BIOS. The BIOS also auto detects and configu […]
Show full quote

TrashPanda wrote on 2023-03-07, 13:58:

98 is a picky bitch and can do this with any hardware changes, that said are you sure the CPU is working ? you may have a bad CP […]
Show full quote

98 is a picky bitch and can do this with any hardware changes, that said are you sure the CPU is working ? you may have a bad CPU.

Did you load BIOS defaults ?
Check to make sure you are on the latest version of the BIOS ?
Check the Dip Switches to make sure they are set correctly for the 1Ghz CPU ?

You may have to do a Fresh install of 98 to see if that fixes it ..98 never did like hardware being swapped around.

The motherboard has "dipswitchless mode" which means I can set up everything in the BIOS. The BIOS also auto detects and configures everything correctly as far as I can see. It's a pretty darn good motherboard to be honest - it was the main reason I bought the PC.

For BIOS update: I prefer NOT to update an old BIOS unless I've ruled out everything else. According to the manual and other sites, the BIOS does not need an update to accept the CPU - the BIOS itself is from late 2000 so the 1Ghz CPU was already released by then.

I wonder if there isn't a tool that lets me test the CPU without having to spend several hours reinstalling Windows 98.

You have pretty much ruled out the board side fo things so that just leaves the CPU or 98 as the culprit and my intuition leans heavily on 98 just being a prick about it.

try with 100mhz fsb, try another 133 fsb cpu

rasz_pl wrote on 2023-03-07, 14:33:

try with 100mhz fsb, try another 133 fsb cpu

My other 800mhz CPU had almost the exact same settings except for a different multiplier (6x instead of 7.5) - it worked perfectly.

I'll just reinstall Windows 98 and see where that gets me.

Honestly, Windows 9X is always such a pain in the ass - it's so picky and incredibly easy to screw things up. I already had to reinstall Windows 98 because for some reason Direct X 8.1 could not be properly installed and nothing I did fixed the problem.

I never experienced win98 needing a reinstall for cpu change, this is especially unlikely when changing for same vendor/family cpu.
One thing that comes to mind is badly adhering heatsink. Iv seen few 370 fitted the other way around back in the day 😀 with socket A that resulted in fired CPU, freezes with Intel. Might be emergency thermal shutdown.

rasz_pl wrote on 2023-03-07, 16:41:

I never experienced win98 needing a reinstall for cpu change, this is especially unlikely when changing for same vendor/family cpu.
One thing that comes to mind is badly adhering heatsink. Iv seen few 370 fitted the other way around back in the day 😀 with socket A that resulted in fired CPU, freezes with Intel. Might be emergency thermal shutdown.

In BIOS it shows 33°C which is very low. Unless it spikes while running Windows it's very unlikely. In Windows safe mode, it doesn't heat up either.

I'll still try a reinstall of Windows 98. I have another 120GB SSD anyway. I have ordered the exact same CPU (same model number) just in case for €22 and it should arrive in a few days. If that one works, I can ask for a refund. For all I know, someone had their OC fun and fried the CPU ...

red_avatar wrote on 2023-03-07, 16:57:

rasz_pl wrote on 2023-03-07, 16:41:

I never experienced win98 needing a reinstall for cpu change, this is especially unlikely when changing for same vendor/family cpu.
One thing that comes to mind is badly adhering heatsink. Iv seen few 370 fitted the other way around back in the day 😀 with socket A that resulted in fired CPU, freezes with Intel. Might be emergency thermal shutdown.

In BIOS it shows 33°C which is very low. Unless it spikes while running Windows it's very unlikely. In Windows safe mode, it doesn't heat up either.

I'll still try a reinstall of Windows 98. I have another 120GB SSD anyway. I have ordered the exact same CPU (same model number) just in case for €22 and it should arrive in a few days. If that one works, I can ask for a refund. For all I know, someone had their OC fun and fried the CPU ...

Yikes don't trust the BIOS thermal sensor to be accurate, especially on boards as old as these. Take it with a pinch of salt it could be close but just as likely its not, gently touch the CPU while its running, if its hitting thermal overload you'll know pretty fast.

I don't think Slot1 can read the thermal sensor on Pentium III CPUs? (Edit: I was confused by 'slot 370' in the OP. Was thinking this was referring to a Slocket.)

Also is an aging VRM possibly the culprit?

Most likely the PSU or motherboard capacitors.

You can also try reseating the CPU. Could be that the pins are oxidized and need a couple clamping/unclamping cycles to get a good connection.

Most likely the faster CPU is stressing the system more than it can handle due to age. When you go into Windows, the stress is there unlike when in BIOS. I'm with cyclone3d on it being some old caps which may not be leaking but just bad. There's no way Windows 98 has an issue with that processor swap.

OK I did a bunch of testing:

- reinstalling Windows 98: no difference
- resetting BIOS: no difference

Then I saw an error message in the BIOS: BIOS update date incorrect. CPUID=0000068A

I googled this and apparently it means the BIOS doesn't recognise the CPU code so I decided to flash it to the final version, reset to default settings, reconfigured everything and ... Windows 98 suddenly booted fine.

So I installed 3DMark2001 SE because I wanted to compare benchmarks with my old 800Mhz and wanted to do some OCing (I have a high end fan on the heatsink that is way better than the original fan - the CPU never goes above 34°C).

About half-way through the benchmark ... POOF ... system shuts down again.

The thing is, I can't even restart the system until I cut off the power and hold the power button to drain the remaining power. It's definitely NOT a software issue. I figure someone probably had their fun OCing this CPU and now it's unreliable. I'll ask for a refund. The second one is on the way anyway.

cyclone3d wrote on 2023-03-07, 19:53:

Most likely the PSU or motherboard capacitors.

You can also try reseating the CPU. Could be that the pins are oxidized and need a couple clamping/unclamping cycles to get a good connection.

These CPUs still had gold plated pins to prevent oxidization. You might be right but the cooler is tricky to remove and put back on so I'm not very keen on repeating this process a dozen times. The motherboard is perfectly fine - it has really high quality caps which is why I bought it in the first place (that and because it was a high end mobo at the time so has lots of bells & wistles).

The PSU it's definitely not - it's a modern modular one and the voltages are extremely stable not to mention that it's WAY overkill for this PC. Since the PC worked perfectly before, there's nothing to point towards the PSU. Pentium IIIs were pretty efficient CPUs which is why you can OC them so easily.

Unless you test the chip in another motherboard, then you can't rule out the motherboard.

red_avatar wrote on 2023-03-07, 21:01:

About half-way through the benchmark ... POOF ... system shuts down again.

did you touch the cpu immediately after? not the radiator but cpu/socket

red_avatar wrote on 2023-03-07, 21:01:

The thing is, I can't even restart the system until I cut off the power and hold the power button to drain the remaining power.

still sounds like thermal shutdown

red_avatar wrote on 2023-03-07, 21:01:

I figure someone probably had their fun OCing this CPU and now it's unreliable. I'll ask for a refund. The second one is on the way anyway.

Have you _ever_ seen such mythical processor? and I mean saw and not read about it on forums.

Report back here when you get the new CPU and test it out.

Also, what's the S-code on the 1Ghz CPU you have that's giving you problems?

Your cpu will be running off the 5v rail from the PSU. I'm amazed no one has yet mentioned that modern PSU's do not provide many Amps on the 5v rail as
everything after P4 and Athlon 64 uses the 12v rail.

Can You please give us the PSU 5v Amps rating? You could try dropping the fsb to 66mhz to underclock the cpu and see if this makes a difference.
I remember back around 2004 trying a Radeon 9800xt in my old AMD Duron setup, it wouldn't boot. Years later with a more powerful power supply and
no probs whatsoever.

Imperious wrote on 2023-03-08, 00:24:

Your cpu will be running off the 5v rail from the PSU. I'm amazed no one has yet mentioned that modern PSU's do not provide many […]
Show full quote

Your cpu will be running off the 5v rail from the PSU. I'm amazed no one has yet mentioned that modern PSU's do not provide many Amps on the 5v rail as
everything after P4 and Athlon 64 uses the 12v rail.

Can You please give us the PSU 5v Amps rating? You could try dropping the fsb to 66mhz to underclock the cpu and see if this makes a difference.
I remember back around 2004 trying a Radeon 9800xt in my old AMD Duron setup, it wouldn't boot. Years later with a more powerful power supply and
no probs whatsoever.

The wattage difference between a 800Mhz P3 and a 1Ghz P3 isn't nearly enough to cause that issue, the system runs perfectly with the 800Mhz so the chances of it being 5v issues is highly unlikely. This has all the hallmarks of thermal overload and the CPU is shutting down to protect itself.

Pentium 3 socket 370 systems also don't have the PSU issues that plagued the early Athlon setups, their wattage requirements are really no different than what a Pentium II would require, heck you could run a P3 setup off a 350watt PSU even with a weak 5v rail ~18-20 Amps. (The GPU might not like it but the core setup wouldn't care a bit)

I still think it is the PSU or capacitors on the motherboard.

Only way I see it being thermal shutdown is if the heatsink isn't on the CPU flatly.