Why will some old motherboards refuse to work with some graphics cards?

Hi all. I have an IBM Aptiva 2158 with a V72MA motherboard and a K-6/2 processor running at 500mhz. I recently tried to install a Radeon 7000 PCI to no avail - won't get past POST. I've tried pretty much everything, such as setting the graphics card to "Auto" in the BIOS (should fall back on the onboard ATI Rage Pro, but doesn't), manually assigning IRQs, you name it. The card has been verified to work, but this computer seems to have a problem with it. There is definitely enough juice in the system as I am using a 400W PSU. The PCI slots do work and I've tested that with a Soundblaster.

At this point, I think it's pretty much a given that this card will not work in this motherboard. Despite being generally period-correct and PCI 2.1, which this motherboard supposedly supports, it won't work. I was wondering why, from a technical standpoint, this would be the case. My question is probably more academic than technical at this stage since I don't think it's possible to get this card working in this system.

 

Hi! Thanks for your reply. I tried flipping JP1, the VGA interrupt, but it didn't seem to change anything either way. I'm still kind of unsure what a "VGA Interrupt" does anyway.

The board's manual claims that there's a JP4, an ATI Rage Interrupt, but it's not on the board diagram nor is it on the board itself. I'll take a look at bus speed and report back.