One last thing I remember is maybe playing with the PnP OS option if it exists: See
this KB article.Don't remember seeing this option in the BIOS, but will check again! Thanks for the heads-up!
Do yourself a favour and configure it on a linux machine.
Use kernel parameters to disable ACPI and self-assign IRQ's to each GPU (ACPI can stuffup horribly for some reason with so many GPU's)
Ive had 8 GPU setup like this temporarily but it really puts alot of strain on the board and I could literally feel the slots heatup with all 8 running thus I dont really support this for a stable longterm setup.
I did attempt to set everything up in Linux initially (Ubuntu 12.04) but I remember having problems getting it set up properly with the drivers and having the cards show up as being available for mining. I suppose I could sink some time into it and use Ubuntu 10.10 like I used to. Hm.
Also, if I set everything up with Linux, I doubt I could underclock the RAM as much as I do in Windows (thanks to a "bug" in the beta versions of Afterburner). I guess I could BIOS edit
since the 7970's don't do hash checking like the 6XXX series and below did (not a lot of people know this.. including the guy that makes RBE, sadly), but thats very uncharted territory at this point, and not many people have attempted it. Also, I've set the SATA type to AHCI in the BIOS as opposed to ACPI.. is that fine? Or should I configure things under IDE?
Go in your BIOS and disable EVERY non-essential piece of hardware that you wont be using.
Did that. Disabled everything but USB, then disabled USB and gave that a try. Didn't help.
Also, using 16x > 16x risers may be causing a problem, because your board is trying to negotiate to 16x speeds. Some boards, when negotiating to max slot speed, will turn off other slots entirely in order to have the full amount of bandwidth available (PCI-E lanes are not unlimited). Try using 1x risers across the whole shebang. If you have limited 1x risers, use the 16x risers in your PCI > PCI-E adapters since they are always 1x speed.
Seems reasonable. When all cards are plugged in via risers, I noticed that the two cards that weren't available for mining were (incidentally?) the two 16x connected cards. Could I just cut the part of the cable that makes the whole thing a 16x cable so that there are only enough connected wires for it to function as a 1x to 16x, and use the cable as a 1x to 16x cable? I'm willing to sacrifice a cable to make this all work! For science!
Also make sure your risers are not defective.
The risers aren't defective; I unplugged two 1x to 16x cables from two other cards, and after a reboot all of the remaining cards were recognized and functional (including the 16x cards, which were not functional before).
Powered shouldn't matter if you are doing underclock/volt. Also, I already have experience with 6 cards on 1 board as well as using PCI > PCI-E adapters (I'm using one in a 4 PCI-E slot board now, now have 5 slots).
But I'm
not underclocking/undervolting, quite the opposite, I'm
majorly overclocking and
majorly overvolting (1231mV, 1270MHz core).
Oh, almost forgot. You say you are using 2 PSU's. If you can, power on the PSU that ISN'T powering the motherboard FIRST, then the one that does SECOND.
Way ahead of you; I'm using this bad-boy: