Are they all plugged in to monitors or not? Just 'coz I think your BIOS will go to PCI first for vid and say, yay PCI vid, oh no, no monitor detected, then go to next card, which is PCI again, and see no monitor connected either, and since 2 seems like a lot to a computer, it's like 10, gives up. There's a trick with a 75 ohm resistor between green and ground I think it needs to be to make a machine think a card is active. Google it though, I'm blanking on deets.

Thanks for the reply.
The additional PCI card I need to connect at the moment is just a SBLive! not another VGA card.
In any case I've tried with multiple PCI cards, same result, I cannot reboot this PC as soon as I connect another PCI card.
The BIOS has been set up to initialize AGP first.

In any case, I've also tried with a PCI VGA card and I still have the same issue.
I couldn't find information about the mod you mentioned.

*Edit* I've also tried with a PCI VGA card + AGP card connected to a VGA switch ... same behaviour. It doesn't matter if I initialize the PCI or the AGP first. If I select PCI first on the BIOS it uses it, but I have the same issue when I try to reboot.
The same happens if I select initialize AGP first, the video signal goes through the AGP card, but when I try to reboot ... yeah , you guessed it!

Ohhh, thought you meant another gfx card, gotcha. Times when I've had something similar, it's been when it's got it's tiny little ACPI brain scrambled and it needed a CMOS clear and battery pull for a while to get it's panties unknotted. But, another thing to consider is how many PCI masters the chipset supports and whether you're using the non-master slot, which also may have only one or two IRQs available to it, which are maybe restricting the pool those cards can use, and they're both picking the same one, due to slot positions and card/driver limits. Then if things aren't starting to improve with those considerations we should start worrying about motherboard hardware issues.

how about you trigger the no picture issue and then unplug monitor from computer and power for 10 seconds and plug it back in

So I fired up my SY-5EMA PRO, because I do know it has an issue. Well, all I can tell you for mine is that it might be sensitive to either the memory installed or the voltage regulation coming from the power supply. But it seems to be mostly pointing something connected to the memory. I don't think I mentioned it to you, but it seems that these boards could have something going on with the memory slots. I've seen others report the same. For me it is slot 2 doesn't seem to fully be in contact with the ram, but if I use other slots it works, usually. Sometimes I have to press reset after cold boot.

I'm not sure what your issue might be. I stuck in a sound blaster live next to a pci matrox card and it works fine rebooting.

I would check the dimm slot situation, maybe only use one slot if you are trying to narrow things down.

Oh btw, the manual says this about no video. I've never seen the first option and press insert? The second option (run outside of case) is something we did back in the day with these super socket 7 boards, which I have seen show a difference. Some cases are BAD for EMI at these clock frequencies.
"To isolate the problem do the following: 1. Press and hold down on the “Ins” (insert) key while turning on the computer until you get video. If you do not get video then, 2. Double-check jumpers setting on you motherboard and remove all add-on cards, unplug all hard-disk and floppy-disk drive cables and see if you can hear some beeps. If you still do not get any beeps, then try putting the motherboard on the table (to isolate it from the case) with the CPU and speaker only, and give it one more try."

I probably should try option 1 and 2 a bit.

Hey folks, thanks a lot for all the replies and help!

Happy to report, it's running like a charm, no issues whatsoever 😀 I can reboot, shutdown... works every time.

So, what did I do? Well, basically, I replaced the CPU 🤣
I just got an AMD K6-2+ 533Mhz that requires 2.0V to work. The previous CPU was a K6-2 running at 500Mhz that needed 2.2V.
As soon as I swapped the CPU, I've got everything working (not sure why, to be honest). Attached is how it looks right now. As you can see the PSU is a brand new one (same as it was before), I'm using the same memory modules in the same slots.
Right now there is a SBLive! connected alongside a PCI network card (Realtek) and a Geforce 2 GTS AGP.
I even tried with a PCI VGA card + the AGP one (and the SBLive! and network card), all working perfectly. I was able to configure the PCI VGA as primary in the BIOS, so if I see any weird things with the AGP can revert to a PCI VGA for DOS games... well that's the plan anyhow...

The build is not yet completed. I've some things en route, a Geforce FX and a Yamaha ISA sound card. It's gonna be fun managing all those IRQs!

Another question, if I may, the new CPU is a K6-2+ 533Mhz that I have configured at 550Mhz (5.5x - 100Mhz) with the same voltage. I guess that should be fine, right? I haven't seen any issues so far.

Thanks again!

Apologies, forgot to reply.

the3dfxdude wrote on 2022-10-11, 02:42:

So I fired up my SY-5EMA PRO, because I do know it has an issue. Well, all I can tell you for mine is that it might be sensitive to either the memory installed or the voltage regulation coming from the power supply. But it seems to be mostly pointing something connected to the memory. I don't think I mentioned it to you, but it seems that these boards could have something going on with the memory slots. I've seen others report the same. For me it is slot 2 doesn't seem to fully be in contact with the ram, but if I use other slots it works, usually. Sometimes I have to press reset after cold boot.

Interesting. That never happened to me. As part of the trial and error process, I even used different memory modules; a single stick (different to the ones that are installed at the moment) was tested in every single RAM slot. Didn't help.

the3dfxdude wrote on 2022-10-11, 02:42:

(...)
Oh btw, the manual says this about no video. I've never seen the first option and press insert? The second option (run outside of case) is something we did back in the day with these super socket 7 boards, which I have seen show a difference. Some cases are BAD for EMI at these clock frequencies. (...)

Yeah, saw that note but never tried that approach as the new CPU arrived. All the problems were gone once I installed it (see post above).

Thanks again the3dfxdude!

New CPU is lower power, that points to your caps going marginal.... If you want to confirm put old one back at 3x100 or something for 300 and if it works fine, it wasn't a CPU problem. If it was a CPU problem and you still get it at 300Mhz, then ignore me. But if it wasn't, then you'll probably see this happen again in some months.

Thanks for the tip BitWrangler.

the3dfxdude wrote on 2022-10-11, 02:42:

So I fired up my SY-5EMA PRO, because I do know it has an issue. Well, all I can tell you for mine is that it might be sensitive to either the memory installed or the voltage regulation coming from the power supply. But it seems to be mostly pointing something connected to the memory. I don't think I mentioned it to you, but it seems that these boards could have something going on with the memory slots. I've seen others report the same. For me it is slot 2 doesn't seem to fully be in contact with the ram, but if I use other slots it works, usually. Sometimes I have to press reset after cold boot.

Hey, sorry for recovering this post again.
I just experienced the weird memory issue you described. I've got a Kingston KVR100X64C2/128 (128MB PC100) memory module. It turns out, this guy only works in slot #3, I get constant beeps if I install it in any of the other 2 dimm slots. I've several memory modules of different capacities, this is the only one that has shown this behaviour.

I'm still working on my build, I hope I can post something soon enough.

Thanks all!

I have a 500 MHz K6-2 and a 500 MHz K6-2+. The board came with the 500 MHz K6-2, which did not work correctly, but worked in every other processor I tried (from dual voltage P-MMX 233MHz, K6-3 333MHz). So I thought it was the processor. Hard to believe it is a specific voltage -- I think I remember checking the voltage output, but maybe I'll hook a scope to it if there is no other reason for this behavior. I'll check it out sometime and inspect the memory slots some more.

That sounds great.
Thanks!