I've got a system set up with 3 PCIe cards (all the same Matrox Millennium P650 PCIe)- scanpci and lspci only show the one at 05:00.0.

I've messed around with various kernel compiles (2.6.21) as well as looked around the bios.

I want to set up multiple displays, but can't get the system to see the other two cards. (Nothing in logs or dmesg either.)

Any ideas on where to start? Been google'ng and searching here.
Thanks,
Eric

Just a couple quick ideas, going from memory here -- if you still have the problem tomorrow, I'll look into detail into what my first suggestion is and post some more:

1 - Read up on your boot-loader (LILO or GRUB) and see about pci= options you might be able to specify on the boot prompt, or 'append' into the boot command from the boot-loader, something about forcing detection of devices. Sorry I can't be more precise at the moment, but I will look into it as I said.
2 - Just an idea, but have you tried editing your xorg.conf and specifying a(nother) specific "BusID" in the device section for (the) card? Replace the BusID PCI:5:0:0 (or add it) with another bus address, and see if it picks up on another card. (It may be easier to install only one card at a time, in each of the different slots, and then check lspci, scanpci, lsdev, and lshw to get a fix on the exact bus addresses of each slot).
NOTE: if you don't have LSHW you can get it from Sourceforge.net.
Best of luck