Hi Vogons community.

Need help with troubleshooting an unstable motherboard.

Recently I had to move to another country for some time and had to leave my retro "lab" with tons of equipment and old hardware behind. So first I rebuilt my Asrock Frankenstein agp+pcie build more or less successfully, albeit I have grown somewhat tired of it due to weird VIA chipset quirks.

Also, these days I don't see any point in building such an overkill system for primarily Win98 and very early XP gaming, so I wanted to dial it back a bit and improve compatibility going with Intel 875p chipset.

I've managed to win an Asus P4C800-e motherboard with CPU and a ram stick on eBay for a reasonable price and quickly built a system around it. But then it all went down to hell. It's somehow totally unstable and troubleshooting the motherboards is a total nightmare as you all know.

So the case is:
Asus P4C800-E Deluxe with P4 2.8ghz (prescott) posts okay and 98% of time runs fine in BIOS settings. As soon as it begins booting, it's getting more and more unstable until it freezes.

Win98 install hangs on the first progress bar right after Scandisk is finished doing its thing (wait while windows prepares the installation or something like that, hangs on 100%, system freezes). Memtest86 boots and starts checking the memory then hangs randomly after a couple of minutes, no errors thrown, system freezes (moving ones and zeroes or something). Quite often the motherboard could hang during post on "checking NVRAM..." line or sometimes moments before that and sometimes later where the IDE controller goes through initialization.

Well, you've got an idea. No matter which boot device I use (floppy/cdrom/hard drive sata or IDE), no matter which onboard devices enabled or disabled - the situation is mostly the same. It all ends with giant freakin freeze.

I've tried swapping GPUs (i've got only Geforce 5700LE and Geforce 5950ultra), power supplies and ram sticks (I've gone one that's corsair 1gb DDR400, and then tried couple of different sticks of DDR400 of different capacities, mostly 256mb; also tried different ram slots).

The motherboard was advertised as "everything tested until bios, works fine, one USB port is not working". I've tried disabling the USB controller and this didn't change much.

One time I was able to witness the following phenomenon: the motherboard was sitting in BIOS and then after 5 or so minutes everything started slowing down to the point of being absolutely non-responsive. GUI tabs were switching veery slowly, screen was refreshing line by line. Some of the popup menus took 10-15 seconds to render. It was really trippy though I'm not sure it has something to do with the main problem. Might've been some sort of a BIOS bug.

Thermals are fine according to BIOS (around 45c-50c on idle for 2.8 prescott is fine, right?). I tried buying another cpu, which is 3.2ghz Northwood, but the motherboard unfortunately doesn't POST with it. Maybe the CPU is a dud, I have nothing to check it on.

So, as I said, no proper equipment or spare parts or other systems to test everything properly. I only know that both GPUs work fine with Asrock's motherboard. Nothing else. Come to think of it, I can also test the DDR modules as the Asrock's mobo has DDR1 slots. Though I don't think that all 6 DDR1 modules I've tested could exhibit the same behavior.

The motherboard itself looks fine. No visible damage or bulging capacitors.

So I'd be really grateful for any advice, tips or shared experience with similar symptoms, even as generic as "have you tried to clear NVRAM" or something. I'm really at the loss here and I'd really love to get this motherboard going 🙁

EDIT: Oh, and I also replaced the thermal paste on the southbridge under the heatsink. Was thinking that maybe it overheats or something. But that didn't help either.