GTX 1080Ti works in SLI but not video output/failure solo?

[DavidVioMC]

I bought a cheap reference nvidia GTX 1080Ti on Craiglist to SLI since 1080Ti's are now cheap enough to be worth SLI'ing and I have been running a single reference GTX 1080Ti for a while now, I went to the dudes house and he said he bought two GTX 1080Ti straight from Nvidia 3 days after they were out and he had invoices and original boxes and everything and had them SLI'ed ever since, he even showed me the card working and benchmarked it infront of me before pulling it out of his rig, he said he pre-ordered a RTX 2080Ti and wanted to sell one of his 1080Ti's to make back some of the money he spent on the RTX 2080Ti, everything checked out so I bought it.

When I got home, first I plugged in the bought 1080Ti without SLI bridge to check if BIOS is up to date, the card was not showing up in Device Manager nor in Nvidia Control Panel, so I pulled out my card and swapped the bought card into first PCIe slot instead and turned it on, I was getting no video and my motherboard was beeping an error, I check the manual and it comes back to "GPU utilization Failure", I tried the card in a different computer and it also failed to post and showed an error code which came back to "GPU failure". So I decided to go back to my rig and plug in the card as slave card just like the guy did and plug in SLI bridge, my PC booted up and both cards showed up in Device Manager and Nvidia Control Panel, so I decided to turn off my PC and take off the SLI bridge and my PC still booted but with a different error "GPU in Slot 4 utilization Failure" and the card was not in Device Manager or Nvidia Control Panel but my card in first PCIe slot was.

So I turned it off and put back on the SLI bridge and no error on Post and both cards were in Device Manager and Nvidia Control Panel so I decided to enable SLI and no error, I went into CSGO and both cards were sitting around 30-40% usage and the game worked. I decided to benchmark both cards in SLI, after 2 hours of benchmarking, both cards were sitting at 80% usage with similar temps, same clocks ect. with no crashes.

I decided to take the card to a local IT shop for them to test it incase I'm doing something wrong, they said the card is bricked and does not want to post, I told them to try SLI the card and see if it boots and of course it did with an SLI bridge, it was detected in Device Manager and the card worked perfectly fine in SLI. It seems the card does not work without SLI bridge. They told me it could be because someone installed a modified BIOS that could only be for slave cards in SLI. I went back home and checked the bios and it comes back to the latest GTX 1080Ti BIOS version so I'm confused, is this a defective card or modified one? The dude I bought it off didn't tell me anything, it could be well a defective card and since he had them SLI'ed ever since, he never noticed his slave card doesn't work without an SLI bridge.

 

[Killer01ws6]

Well, there is most definitely something amiss here.. I would have felt good about your pre-checks and your TS is solid, never seen a card that could not talk unless SLI bridge was on though.. It does seem something has been modded on it or a partial failure. I would go back to seller for a full or partial refund, partial if you keep the card and you are getting SLI results, but yea... only other option is send it back to Manufacture for repair. I did not catch, what make card is it.