[IMAGE] The x3 red 6pin ports on the PSU run power to the CPU 8pin (up behind the heatsink, top middle of board) & in the lower right hand corner is the GPU/PCIE_PWR 8pin, so you have two solid 8pin (EPS/CPU) cables (CPU is long, PCIE is short) sending power to the mthrbrd, make sure PCIE_PWR 8pin is connected to mthrbrd & to PSU Search 800GY on eBay for a replacement If you want an aftermarket PSU, if it's 1200watts or more it will come with two CPU cables & two CPU 8pin ports to plug into the front panel, one will go to your CPU 8pin header (behind heatsink), one goes to PCIE_PWR 8pin (lower right)  If another 800GY, or an aftermarket PSU won't cure this, you can sell it afterwards, after testing, since they can retain resale value (though u may lose a little money back relative to what u paid). Or try Amazon/MicroCenter/Newegg & return it if it won't cure this Then suspect the motherboard  *Your 24pin 3.3v/5v/12volt readings all look normal, in-spec *Try the GRFX card in different PCIE slots, if u haven't already *We can be sure that dual-2080Ti was an option (on 51 R5 at least, which is about identical to R4), I can't say what your issue is, or the why of it, but when in doubt, post at the EVGA forum also, someone w/2080Ti may have heard of this happening & have advice
The issue is when I use a non-OEM video card such as the EVGA 2080 TI, it draws more power than the stock OEM 1080 TI, which causes the computer to shut immediately when the EVGA 2080 TI goes under load. I have a 1500-watt power supply that is showing an overvoltage of 12.62 volts on pin 24. This is .02 volts out of specifications and the computer is not even attached to the power supply during this test, so the power supply is not under load. It should be enough for Dell to replace the power supply, but they will not because the computer passes all the diagnostics using the OEM card. Dell will not fix my issue, even though I was told when I bought the $5000 computer that it was fully upgradable and could easily support a two-way SLI due to the 1500-watt power supply. So much for a spending $600 for a  5 year service plan. I have the service manual, but it does not give me the specifications of the type of power cables that connect to the motherboard and other peripherals. Has anyone successfully replaced the OEM Alienware power supply with a third-partyversion?
Area-51 R4, replace PSU with 3rd party one?