I would crack open that FSP PSU as the first thing then. Older FSP PSUs are notorious for developing bad capacitors. If it's an APFC unit, it could be the APFC cap too.

Other than that, I don't see anything on the motherboard that could be causing this. FWIW, I have two similar Gigabyte motherboards (one is a 8ipe1000-G and the other is a PRO-G) and didn't encounter any such issues... or at least not with the PRO-G - I used it briefly to test some of my newly acquired AGP video cards, and had not problems with 4x or 8x cards (the non-pro board has been awaiting trace repair... for a few months now. 😜 ) That said, the PRO-G did need a recap prior to working properly, as all of the CPU VRM output caps were blown (6x KZG 6.3V 3300 uF, IIRC.) These old Gigabyte motherboard do also suffer from bad caps occasionally, depending on what Gigabyte installed on them at the time, so slight chance that might be the issue too. How are the caps looking on your board? Any brown UCC KZG caps? Nichicon HM from 2001-2004 in 6.3V ratings are also affected (look for black Nichicon HM with date codes beginning with H01xx through H04xx.)

Thanks for the suggestion, Momaka. Funny thing is that I am also from Bulgaria. Small world. Ба ли му майката що стана с тва дъно?

SOLVED: Turns out the capacitators near the AGP slot on MB were half-past dead and providing only voltage for a very low-end GPU without 12v FAN at a AGP x 2 rate as the GeForce 2 MX400 passive cooling... Anything more power hungry than that and it's gone directly to a non-responsive black screen. The PSU unit was my first guess, but it is the best make in the world Fortron (FSP Group) proved to be everlasting, tested with no problems whatsoever.

Just ordered the same Gigabite, but the 8IPE-1000 PRO-G rev. 3.1. Are they any good? Seller tells it works perfect.

I ended up with a Gigabyte 8IPE1000 Pro a few years back, and it had a quite a few bad caps. I replaced them with Rubycons and it worked great.

I think for boards of this era there is always a chance to have bad capacitors, either straight away or after a short period of time. Maybe it's a good time to learn about replacing them.

AndrewRus wrote on 2025-12-02, 21:30:

SOLVED: Turns out the capacitators near the AGP slot on MB were half-past dead and providing only voltage for a very low-end GPU without 12v FAN at a AGP x 2 rate as the GeForce 2 MX400 passive cooling... Anything more power hungry than that and it's gone directly to a non-responsive black screen.

Time to fire up the soldering iron then. 😉
Probably all of the capacitors from the same brand and series on that board are at a similar state at this point.
It's a shame so many of these boards probably got tossed out due to the bad caps, though. They are pretty reliable otherwise.
I also got several socket A motherboards from Gigabyte from the same era, and 2 of those needed a recap as well. Luckily, I still have some capacitors left in my stash... but will need to re-order some soon. Some of these old boards are eating them up fast.

AndrewRus wrote on 2025-12-02, 21:30:

The PSU unit was my first guess, but it is the best make in the world Fortron (FSP Group) proved to be everlasting, tested with no problems whatsoever.

FSP is -OK-. A lot of their PSUs come with average capacitor brands like Teapo and CapXon... occasionally OST too on the newer units. All of these tend to do OK overall... but compared to good Japanese cap brands, their failure rate is still much higher. So about 1 in 5 units will need a recap eventually. The good news is that many still made it to 5-10 years or service, so certainly they are decent PSUs.

AndrewRus wrote on 2025-12-02, 21:30:

Just ordered the same Gigabite, but the 8IPE-1000 PRO-G rev. 3.1. Are they any good?

It's probably going to be very similar to the Gigabyte board you have now. I don't recall what the differences were between my G and PRO-G, feature-wise. They look very similar too.

AndrewRus wrote on 2025-12-02, 21:30:

Seller tells it works perfect.

Sadly, most sellers don't know too much about bad capacitors. So as long as the board appears to turn on OK, they will list it as working.
In any case, I hope at least your new board has caps that aren't from the affected series. Knowing Gigabyte boards from that era, though, there's really only a 30-ish % chance of that happening. Reason why is because most of the time, they used the abovementioned cap brands and series, e.g. UCC KZG, Nichicon HM, Sanyo WG, and Rubycon MBZ. Of these, only MBZ are known to be good. Sanyo WG is mostly OK, but occasionally can burst if not used in a long time. And KZG and 2001-2004 HM are pretty much a guaranteed failure at this age.

AndrewRus wrote on 2025-12-02, 21:30:

Thanks for the suggestion, Momaka. Funny thing is that I am also from Bulgaria. Small world.

Привет!
Не знам да ли светът е малък, или просто ние българите сме много пръснати на всякъде.
Но радвам се че виждам пореден сънародник тук! 😀

AndrewRus wrote on 2025-12-01, 22:29:

I am building a Pentium 4 s.478 rig that runs fine with a GeForce 2 MX400 64MB Agp x4. Everything runs great until I install a more "powerful" GPU card. The system won't power on all! Just like it is unplugged from the cable, pressing the power on button does nothing! No fans spinning, no beeping... As soon I install Radeon 9600 128mb/128bit Agp8 this happens, won't start. Tried with a GeForce 4200ti 128/128 8xAgp. With it at least the system turns on, CPU fan spins, but graphics card's fan won't spin and no boot or beep at all, just black screen. As soon as I return the GF2 everything is back to normal and games play as they should. The 9600 and 4200ti are tested and in perfect order. Specs are: Pentium 4 3.2Ghz Prescott, 2x512mb DDR1, MB is Gigabyte 8IP1000 rev2.0., PSU is FSP Group 400W, Win XP Pro SP3. What could be the reason? 🙁

I encountered the same problem on the same Gigabyte board - a broken contact around AGP on the graphics card itself (noname GeForce 2 MX400 32MB). Once I fixed the connection, the graphics card card booted normally.

btw, I like this mobo! I bought it as a student, and ~20 years later, it still works without any issues. I wouldn't recommend using it with any Prescott processors, they're quite hot and heat up motherboard's VRM. I switched from P4 3.2GHz Prescott to P4 2.8GHz Northwood, and it's about half as cool.
Intel PAT is supported and can be enabled in a hidden BIOS menu (Gigabyte's "M.I.B." option as I remember), which gives some RAM acceleration (requires FSB800 and DDR400).

As for FSP power supplies, they all require maintenance; 5 out of 5 FSPs (250-450W) in my collection have capacitor issues.