One such experiment came from Reddit user Zimtok5. He demonstrated in a video clip that he was able to set up his HTC Vive and Oculus Rift DK2 on the same PC and run two separate games at the same time.
The PC that he used to test this is an Intel Core i7 4790K paired with two MSI GTX 970 Gaming 4G graphics cards, which provide an additional HDMI output. With the extra HDMI output, Zimtok5 was able to plug in his Vive and Rift at the same time, and because the games for the Vive and the Rift launch from different portals (Steam vs Oculus Home, respectively), the games for each can be started without interfering with the other.
SLI? Not So Much
We didn’t want to take Zimtok5’s word for it, so we decided to try running the same test with our Oculus Rift and HTC Vive hardware. We used our standard test system: Intel Core i7-5930K with 16GB of Crucial Balistix DDR4 memory and an MSI X99S Xpower AC motherboard. We first tried to replicate this idea using two GTX 980Ti cards in SLI, a ZOTAC GTX 980Ti AMP! Extreme and a Gigabyte GTX 980Ti Extreme Gaming.
Unfortunately, we were unable to get either HMD to initialize while plugged into the second GPU. The Oculus Home software would not detect the Rift if it was plugged into the second card. Steam VR detected the Vive, but it failed to initialize the compositor unless it was plugged into GPU1.
We were still able to make both HMDs work at the same time, but the second GPU never actually came into play. In order for the Vive and Rift to work at the same time, we had to use the optional Mini-DP port on the Vive’s link box. This allowed us to attach both HMDs to the first graphics card. To be clear: We were running both HMDs off of a single system and a single GPU.
Oculus Home First, Then SteamVR
With the Vive plugged into a DisplayPort output, SteamVR was still detecting the Rift first, and without a toggle switch in SteamVR to select the HMD you want, we had to find a workaround for the problem. The solution is that you must launch Oculus Home before starting SteamVR. When Oculus Home is running, the Rift is already in use, and SteamVR will skip to the Vive HMD when it launches. Curiously, that seems to have solved the problem permanently. We are now able to launch SteamVR first, and it detects the Vive, rather than the Rift.
Once we got passed the HMD initialization problem, everything else just worked. The games both played on their respective HMDs, and the audio for each worked flawlessly.
Frames Per Second - Minimum, Maximum
Average Frames Per Second Over Run
Now that we have this working, we’ll have to go back and do some proper performance analysis to see if this is actually feasible. My gut tells me this won’t work well with most game combinations, but Lucky’s Tale and Vanishing Realms seem to have been working well together. The caveat is that I can operate only one game at a time, so whichever game wasn’t being played was simply sitting idle. I’m eager to determine if you can actually have two people gaming on the same system, and what kind of GPU you need to pull that off.
Update: April 11, 2016, 4:54PM PT: Upon reading some comments we went back and verified that all configurations were tested. We found that the Vive still won't start on the second GPU, but the Rift actually does. You can plug in the Vive through HDMI, as long as it is plugged into GPU1. The error message about the compositor still appears when the Vive is plugged into GPU2.