Multi-monitor support in PC games isn't relatively new, thanks in part to modern GPUs featuring multiple outputs. The same goes for playing in Ultrawide. Back when the original Doom was released, in 1993, the idea of an MS-DOS PC running multiple monitors was unheard of. This makes the game's multi-monitor support pretty incredible because it actually needs multiple PCs running Doom to pull it off.

In Doom version 1.1 the multi-monitor support is done via networking multiple copies of the game, which is what we see here. This was removed in later versions, so what we're seeing here is old-school floppy disk Doom running on authentic MS-DOS 6.22 PCs.

This is a pretty incredible video from Tech Tangents, who manages to network four DOS PCs to run multi-monitor Doom. Weirdly the left and right monitors offer a 90-degree viewpoint with the fourth monitor displaying the map. Odds are no one played Doom like this back in the day.

Check it out.