C16
By follow I mean trace tracks 😀 Use strong flashlight if tracks are going into deeper layers, sometimes one can see second layer this way. At that time mobos were only 4 layers with internal layers taken by ground and power, designers rarely (only bad ones or in desperation) routed in inner layers.
You can take more pictures 😀 But better quality, with lots of either light natural or diffused light (bounced off white background) and phone closer to pcb so everything is sharp without reflections or shadows. Both sides front back.

but before we start tracing simple tests

>5V at one side of the header for the reset button, and 5V at powergood at pin 13
>there seems to be only a 100 ohm resistor between the two

Yes, and what happens when you Press RESET button 😀

The way reset is usually implemented is you have Reset header with:
pin 1 linked to ground, either directly or thru small resistor
pin 2 either pulled to 5V with lets say 10Kohm resistor, or connected to a voltage divider (middle of two resists in series) on power supply Powergood output pin 1 (orange cable), and finally that goes to chipset

Now when you press reset you short 1 and 2 and pull chipset powergood to ground, when you release chipset should generate reset on
CPURST 20 O CPU Reset. This signal resets the CPU processor.
SYSRST 63 O Cold Reset. System cold reset.
SYSRSTJ 81 O Cold Reset. The signal is the inversed cold reset.

does this happen?

>5V at powergood at pin 13
means there should be reset happening on those pins when powering on alone

measure resistance to ground of CPURST 20 SYSRST 63 SYSRSTJ 81 (no idea if this one is used in anything, maybe for HDDs)

Logic analyser says that the only one that moves is powergood, which goes low when reset is shorted. CPURST, SYSRST, and SYSRSTJ never move off low; neither with CPU in or out. I guess this isn't favourable.

Resistance at CPURST is 10K, SYSRST is 110 ohm, and SYSRSTJ is 2.68 ohm.

CPURST sits at 1V all the time, reset or not.

LeeDerbyshire wrote on 2026-10-24, 13:54:

Logic analyser says that the only one that moves is powergood, which goes low when reset is shorted.

so that works

LeeDerbyshire wrote on 2026-10-24, 13:54:

CPURST, SYSRST, and SYSRSTJ never move off low; neither with CPU in or out. I guess this isn't favourable.

😀 its really bad

>Resistance at CPURST is 10K

good

>SYSRST is 110 ohm

bad

>SYSRSTJ is 2.68 ohm

very bad

and the baddest is the fact afaik SYSRSTJ should have opposite logic level to SYSRST.
I would remove M1487 and check resistances on those tracks again, but if you dont plan on investing $20 for the new chipset just to experiment with no warranty that it will fix the board then that would be that.

Pretty much what I imagined after those checks. I don't mind spending a bit of money on an M1487 if it will save an old board; but I'm not very confident that I can solder one back in. Anyway, I'll try and get the old one off and see what happens.

Well, then M1487 is off, and I haven't wrecked anything that I can see. The CPURST resistance is still 10K (no CPU fitted), SYSRST is still 110 Ohm, but SYSRSTJ is 4 M.

take a good picture of M1487 footprint, and in general zoomed in pictures front and back so I can help with tracking where those signals are connected to 😀
SYSRST still at 110 ohm gives me good vibes that maybe its connected to a 74 series chip that got fried when ISA slot was shorted

I've just traced SYSRST to pin 13 (6A) of a 7404. It's the only 74xx on there. Is it worth taking it out and sticking in the Xgecu?

I hope you can make some sense of these: I'm not really set up for fine photography, and it's getting dark here.

I put a new 7404 in there, and SYSRST is now 4 M. The original IC was 74F04, but I only have LS and HC right now. I'll try the 74LS04 first, and see how that goes. I've a new/old M1487 on order, which I should get in a few days' time.

LS might be good at 25 mhz, the HC might do 33. IDK been a while since I looked up gate propagation delays.

I'll get some F04's in the coming days, just to keep it original. I'll come back with results from the LS and HC, though. It'll be interesting to find out, I think.

U14? it was definitely fried, nice one! its only for buffering reset, any 04 will do

but lets not celebrate just yet 😀 in the mean time measure M1487 you pulled off the board, between its ground and all the reset pins.
Still a slight chance its still alive. SYSRSTJ going from 2 ohm to megaohm is suspicious, but im not sue if anything uses that signal

Meda wild guess - probably a miss but what the hell. I maybe traced CPU reset going under M1489 and maaaaybe going out again between PCI slots all the way near U14 to resistor R49 and then maybe under 74f04. Can you measure resistance or continuity mode between CPU reset C16 and all pins of 74f04 and resistor R49? one probe in C16 the other all those pins.

Okay, will do. It had my hot air gun at 400 C pointed at it for a few minutes, so I'm not entirely certain that it is still compos mentis.

for things you want to live after reflowing its best to keep them for a while at 100C before going in with solder melting temp
extra poins for nozzles that direct air at chip legs only

I'll have a new one in a day or two, so I will at least be able to compare the two. If the old one seems okay, I'll straighten the legs that got bent and put it away for posterity. I had to gradually increase the temp to 400, but I had the air flow on a low-ish setting. The solder wasn't really properly molten, and I had to sort of gently unzip the legs starting at one corner, while hoping not to pull any more tracks up. I say 'more' because there are still three loose tracks that I will have to be careful with.

I saw that, same corner as the bend pin at the start of the thread, might have been ripped before you desoldered the chip. You can try gluing them to pcb if you have soldermask or a high (very) temp glue.

The system stays in Reset when the 'CMOS Clear' jumpers are connected also. Have you checked those? They are near the BIOS on this board.

MikeSG wrote on 2026-10-27, 12:49:

The system stays in Reset when the 'CMOS Clear' jumpers are connected also. Have you checked those? They are near the BIOS on this board.

J17 Jumper is in correct 1-2 position.

In designs I am familiar with (like this one) clear cmos doesnt hold cpu/chipset in reset, it pulls RTC battery supply to ground clearing its contents. Then when BIOS executes one of the first things being checked is RTC register 0Dh bit 7 battery good and oEh bit 7 'RTC lost power'. I call those CMOS_0Dh_REGD_Battery_Good CMOS_0Eh_CMOS_Diag_RTC_POWER_LOST in my custom headers.

https://web.archive.org/web/20111209041013/ht … 0Register,-D%20

and Bios designer can decide what to do next. Modern ones seem to initialize CMOS contents and loop in place giving the use a feeling like the PC didnt boot at all and is frozen in reset.

Zenith for example displays "Please replace the back-up battery! +++"
https://github.com/raszpl/Zenith_ZBIOS/blob/a … 3.2C.lst#L19247

DTK first make sure to reset CMOS
https://github.com/raszpl/DTK_BIOS/blob/039a7 … _DTK.lst#L24398
then go "CHECK BATTERY !"
https://github.com/raszpl/DTK_BIOS/blob/039a7 … _DTK.lst#L17936

MikeSG wrote on 2026-10-27, 12:49:

The system stays in Reset when the 'CMOS Clear' jumpers are connected also. Have you checked those? They are near the BIOS on this board.

Thanks for the suggestion, which is appreciated, and is well worth a quick check; but I did make certain that it is in the correct position. It's one of the checklist items in the manual for the board setup and I went through it several times hoping for something I might have missed when it first failed to work.