I've heard from Truup that he ran dedicated just fine with 75MHz Pentium and something like 32Mb of RAM. Map changing lagged badly, but otherwise it was playable.
I ran FunkyDM(6 slots DM) with 233MHz Pentium II with 128Mb of RAM, sometimes map change lagged, but it was kinda rare. After I upgraded to 333MHz Celeron, it worked just fine. OS was Windows ME.