I've bought 3 non-mmx 200MHz pentiums. It's a nice cpu to have if you have any motherboards that don't support mmx cpus. And I think, the lack of mmx instuctions doesn't make that big difference in dos. I believe the main reason that a MMX cpu is a little faster is the 16kb L1 cache memory.

I originally tried putting a 166mhz MMX chip into the old computer but it didn't work. I also tried a 180mhz IDT Winchip (oc'ed to 200mhz) but at 200mhz with MMX and a generous L1 cache, it still managed to perform on par with a 100mhz Pentium; not exactly a speed demon.