Wait, a physical card which has 2 GPU cores on it, is fine.
But the whole "2 eyes so 2 GPU's is super efficient" needs to have a terminator sent back in time to kill that stupid argument's parents. And if that fails, kill the people who wrote it down on the internet
Quoting from Anandtech's article on AMD's LiquidVR tech, regarding Affinity Multi-GPU:
Anantech said:Moving on, we have AMD’s compelling content goal, which is backed by their Affinity Multi-GPU technology. Short and to the point, Affinity Multi-GPU allows for each eye in a VR headset to be rendered in parallel by a GPU, as opposed to taking the traditional PC route of alternate frame rendering (AFR), which has the GPUs alternate on frames and in the process can introduce quite a bit of lag. Though multi-GPU setups are not absolutely necessary for VR, the performance requirements for high quality VR combined with the simplicity of this solution make it a easy way to improve performance (reduce latency) just by adding in a second GPU.
At a lower level, Affinity Multi-GPU also implements some rendering pipeline optimizations to get rid of some of the CPU overhead that would come from dispatching two jobs to render two frames. With each eye being nearly identical, it’s possible to cut down on some of this work by dispatching a single job and then using masking to hide from each eye what it can’t actually see.