big caps would be cpu supply, 1.5V supply is smaller but I cant tell where precisely by just looking at the picture of the board

That board has a universal AGP slot. These are supposed to work fine with AGP 2x, 4x and even 8x cards. But in practice, I have found that this isn't always the case. Detailed info on AGP compatibility can be found here.

BTW, my Abit KT7A board also has one of those universal AGP slots, and I experienced the opposite behavior. AGP 2x and 4x cards would work fine but AGP 8x cards like the Radeon 9550 would not. I also have an MSI GeForce4 Ti4200 which started showing artifacts when plugged into that universal AGP slot a few months ago. However, I recently tested it on a motherboard with an AGP 2x slot and it works perfectly fine there.

rasz_pl wrote on 2022-12-22, 08:20:

big caps would be cpu supply, 1.5V supply is smaller but I cant tell where precisely by just looking at the picture of the board

It has even been recapped before I got it (a bit of a mess around capacitor leg holes), but with some chinese caps. Maybe this instability is their fault...

I've tried further testing yesterday with Radeon 9600 Pro, installed windows fine, but after an hour it started freezing or screen went black. One time it mouse even worked, but I wasn't able to click at anything. I left it 10 minutes, just to be safe if it wasn't doing something that froze screen refresh, but no, it remained like that. Screen frozen, only mouse cursor movable.

Maybe full recap with decent caps would help.

Joseph_Joestar wrote on 2022-12-22, 08:34:

That board has a universal AGP slot. These are supposed to work fine with AGP 2x, 4x and even 8x cards. But in practice, I have found that this isn't always the case. Detailed info on AGP compatibility can be found here.

BTW, my Abit KT7A board also has one of those universal AGP slots, and I experienced the opposite behavior. AGP 2x and 4x cards would work fine but AGP 8x cards like the Radeon 9550 would not. I also have an MSI GeForce4 Ti4200 which started showing artifacts when plugged into that universal AGP slot a few months ago. However, I recently tested it on a motherboard with an AGP 2x slot and it works perfectly fine there.

Yes, it should be universal AGP slot, and by design it is. What's more, I don't even think it supports AGP 8x as standard. In BIOS I have AGP 4x Enable/Disable option.

When I got it AGP 2x/4x cards were working, but were unstable in Win98. Now they don't output an image. Only card that outputs an image of all the cards I have are Radeon 9600 AIW and Radeon 9600 PRO, both are AGP 8x, or better said 1,5V, only.

Perhaps with AGP 8x originally planning to be 0.8v rather than 1.5v, the AGP signalling voltage rails are weak, and an AGP 8x card is just about able to cope with drooping voltages.

While AGP notches can hint at transfer rates, they're really only about hardware voltage support and are there to prevent people from damaging cards/slots with incompatible voltage levels. Joseph left a great link explaining this in detail.

The short version is the original AGP 1.0 spec required devices ( both cards and motherboards ) to operate at 3.3V and to support 1x speeds. Supporting 2x speeds was completely optional. The AGP 2.0 spec was very similar in that 1x and 2x speeds at 1.5V are required and 4x operation was optional. The second notch at the back of the slot was added to prevent hardware damage. AGP 3.0 added the 0.8V signalling, but was different because it requires 8x operation. It's kind of vague about requiring 1x and 2x speeds, but nearly all AGP 3.0 cards support 4x and 8x. And of course there is no notch for 0.8V.

In practice for the cards and motherboard slots, if it has the 3.3V notch it must be able to operate at 1x @ 3.3V and might support 2x @ 3.3V. If it has the 1.5V notch, it must be able to operate at 1x and 2x @ 1.5V and might support 4x @ 1.5V. If a card has both notches ( same for a slot with no notches ), it is required to operate 1x @ 3.3V, 1x and 2x @ 1.5V, and might support 2x @ 3.3v or 4x @ 1.5V. There are a few combinations of cards and slots that would fit together but would be incompatible, but no one made products like that ( at least not in any relevant number ) for it to be an issue you'd likely encounter.

On boot, the board queries the card to find which modes it supports and then it picks the fastest operation mode common to the two devices. If the card is displaying the POST, then it's compatible with the board's AGP implementation. However, this is assuming all hardware in question is following the AGP specs, which not all do. And there are some incompatibilities when using AGP 1.0 boards with much newer AGP cards. Most often it's a case where the mboard BIOS doesn't recognize the card, so it can't negotiate an AGP operation mode between the two. My P2B motherboard won't post when using my Radeon 9000 card, but works fine with a newer MX440 and 380 XGL, so go figure.

If you get no display at all and the computer doesn't even POST, you may have a problem with the mboard recognizing the card. You can try to update the BIOS, maybe it has a beta version that adds some compatibility.

If however you are getting some display, but it's behaving erratically, my guess is either configuration conflict or damage to the card/slot. Change the BIOS to limit the AGP slot to the lowest speed possible ( in your case, disable 4x and see if you can force it to 1x ). A universal AGP slot can also mean just AGP 2.0 support; it doesn't mean 3.0 and 8x.

The other big culprit is whether the mboard can supply enough power to the card. It's not uncommon for AGP 1.0 mboards to have weaker power delivery than a later, hungrier card wants. Outside of that, you may be seeing some memory allocation issues. I've heard about problems ( but never seen them ) where a mboard can't properly address the memory on an AGP card, like it conflicts with the system memory addresses or something.