PC Graphics

[daishi2442]

Howdy ya'll, I have an issue with a 6900 XT that I bought; the thing simply won't turn on at boot - no fans, no lights, just a motherboard VGA light telling me something's wrong.

I have it wired up with two PCIe connectors from my Corsair RM850x PSU, with one of the 8 pins covered by a single (6+2) pin connector and the other 8 pin + 6 pin covered by a different PCIe cable, daisy chaining one (6+2) pin to handle the remaining 8 pin & the (6+2) at the end without the additional 2 pins to handle the 6 pin.

My motherboard is an MSI MPG X570 Gaming Plus, running a 5800X3D on the compatibility BIOS from 3/16/2022. The RTX 2080Ti that the GPU is meant to replace continues to operate just fine, so I know it isn't a problem of bad PCIe slots or a failed cable, as I'm using the same ones when I try to get the 6900 XT to run. I'm kind of at a loss right now.

[GreatnessRD]

Was the GPU bought new or used?  Though I doubt its the problem, have you tried adding that last 6+2 with a separate cable instead of daisy chaining?

[daishi2442]

I purchased it second-hand, but prior to purchase I had the seller show me in their own system that it was working, and they permitted me to run a few benchmarks to ensure I wasn't wasting money on a bricked card. I was satisfied with what I saw, but now that it's in my own system the card seems unresponsive.

I can try adding an additional 6+2 cable, but I'll have to wait for it to arrive - the RM850X which I have is from after the revision where they switched out the 2 EPS / 3 PCIe cables for 3 EPS / 2 PCIe cables, and as such I simply don't have a way to run a third PCIe cable to it right now.

[daishi2442]

Okay, so I was able to find another Type 4 PCIe connector, and used that to run one PCIe cable to each power input on the card - still nothing. I tried popping the CMOS battery to see if something on the BIOS was being weird, but got nothing out of it, GPU still sits idle and unlit, with no indication of life. 

[elstaci]

You need to connect the full 2 x 8 pin connections on the GPU card.

Maybe I misread your Original Post but it sounds like instead of connecting 2 x 8 Pins you have 1 x 8 and 1x6 Pin connection.

The last 2 Pins involves Power to the GPU card. So your GPU card is not getting sufficient power to turn on.

also as mention you need to use 2 separate 8 Pin PSU - GPU Power cables. Sometimes if you Daisy-chain the power cables it overpowers your PSU internal power Rail power range.

EDIT: Just read you last reply to the other User. Your GPU uses THREE GPU Power cables and you only have 2 connected?

If that is the case that is why the GPU card is not working. It needs all 3 GPU power cables connected.

[daishi2442]

All three of the power input ports have cables connected to them. I'm simply using one of the two PCIe cables in use to daisy-chain the 6pin and 8pin, as I have seen suggested. 

[hrpuffnstuff]

If you have all 3 pcie connectors attached your ps is probably too weak or the cold boot inrush current is triggering the PPC.  Put each pcie connector on its own 12v rail without any peripheral power sharing and see if anything changes.

[daishi2442]

How would I go about finding out which PCIe outputs from the PSU are assigned to which rail? The RM850x didn't come with anything but a quick-start guide which is quite devoid of anything to that degree of detail.