r_smp is a variable for enabling multiprocessor support.
I think the original Idtech3 had it because ID worked on a SiliconGraphics multiprocessor workstation back in the day.
The engine had it's problems with multicore altough.
Curious thing is, i just tried enabling it for fun and it worked O_O
A very unexpectet result, yet a very welcome one.
I checked in the task manager, and the game uses up to 6 threads of my 6core-12thread cpu.
I dont know if it really brings performance benefits, but yet it's astonishing
And thanks a lot for the answers so far!