System components:
MSI 970a-g43
FX-4350
2x 4GB DDR3 RAM
GPUs:
6x GTX 1060 3GB
1x GTX 1080ti
PSUs:
1x Seasonic Focus PLUS 850W (secondary)
1x EVGA G2 850W (secondary)
1x XFX 550W (primary, powers the motherboard+CPU+drives)
(All graphics cards are powered by the same PSU that powers their riser, if one is used.)
OS: Windows 7 x64
I am attempting to get the following configuration to work:
(Slots ordered by increasing distance from the CPU)
PCIe x1:
One powered riser to a 1060 (powered by the EVGA)
PCIe x16:
One powered riser to a 1060 (in every case that the system booted, this card in this slot was used for the display, as is expected) (powered by the XFX)
PCIe x1:
One powered riser to a 1060 (powered by the EVGA)
PCIe x16:
The following 4-to-1 splitter, with 3x 1060s and 1x 1080ti installed:
https://www.amazon.com/Ubit-Riser-Adapter-Powered-Extension/dp/B0746H1KY3/The 1080ti and 2x 1060s powered by the Seasonic, the last 1060 by the EVGA.
Each time I attempt to boot with all 7 cards connected, no graphics output is shown on the monitor.
Even more confusing, after reaching a stable configuration with 6 cards (6 can seemingly be reached with any combination of cards and risers), and attempting to boot with a 7th card connected, something gets munged. When I undo the addition of the seventh card, I find that I can no longer boot with 6 cards, a configuration that had just previously worked. Clearing CMOS at this point, does not help.
I find that I can only boot again with 6 cards after going back to 5 cards, clearing CMOS, booting to Windows with those 5 cards, shutting down, and then adding the 6th card before booting once more.
Previous stable configuration, before attempting to install the 1080ti (again, in order of increasing distance from the CPU):
PCIe x1:
One powered riser to a 1060 (EVGA)
PCIe x16:
One 1060 installed directly onto the motherboard (XFX)
PCIe x1:
BLOCKED by the card installed in the previous slot.
PCIe x16:
The aforementioned 4-to-1 splitter was used with 4x 1060s. (All of which worked flawlessly.)
3 powered by the Seasonic, 1 powered by the EVGA.
Additional notes:
I've tested each of the graphics cards, risers, and PSUs individually. The BIOS for this old board is the latest available (with no settings for 4G decoding or PCIe link speed).
I do not believe that the 4-to-1 splitter itself is the problem, as it still works with 4 cards connected to it.
I've been stumped on this for quite some time now, so I'm about ready to accept that 6 cards is as far as I can expect to push this motherboard. Any advice is greatly appreciated!