This is footage of The Witcher 3 running 60fps at 8k resolution. That's 7680 x 4320 pixels. On max settings. Gulp.
If you need to know what kind of monster could run the game like this, here's how Thirty IR got the footage across two PCs, the first for playing, the second for capture:
GPUs: 4x GTX TITAN Xp (2017) 4 WAY SLI @ 2038Mhz / 13358Mhz
MoBo: Asus Rampage V Extreme (X99)
CPU: i7 6950X @ 4.30GHz
RAM: Corsair Dominator Platinum DDR4 3200Mhz (64GB)
GPUs: 4x GTX 1080 Ti 4 WAY SLI @ 2025Mhz / 12110Mhz
MoBo: ASRock Extreme11 (X79)
CPU: i7 3970X @ 4.80GHz
RAM: Corsair Dominator Platinum DDR3 2133Mhz (32GB)
If you want to watch the clip in 8K, you need to select "4320p60" from YouTube's quality settings, though be warned, for most people your device will struggle to even play the video at that resolution.