Tilera makes a cool 64 core CPU, more info can be found here. They have a PCI Express development board that works nicely under Linux, so it definitely needed a Doom port. The port is based on SDL Doom 1.10 which can be found here.
You can run up to 30 Doom sessions in parallel. More is of course possible, but I ran out of screen real estate. Each session runs separately on its own core with its own clock, so they will get out of sync if you control all sessions with the same input. You can select which session to control, see the host code for details. There are some hacks provided for multi-keyboard input, but we never got that to work properly.
I don't intend to do any more work on this (ie. I don't have a loaner Tile64 card anymore), so use the sources as you see fit. Licensing etc. is as specified for SDL Doom.
MultiDoom source code (zip archive)