I was screwing around with ArghRad today (looking for more obscure command line options) when I came across the -threads option.
As far as I can tell, a higher number (2-4 is about as fast as I could get it to go) makes it compile faster, at the expense of using more CPU. I don't think a very high number (above 5) will get you much more performance.
On my new computer, my blitzremake.map lit in 72 seconds using -threads 1
using -threads 2, it compiled in 33 seconds, with a tiny bit of noticable lag in other programs.
I would NOT recommend trying this on older machines. I had a gig of ram and a 3800+ dual core AMD to spare so I don't know how this will affect older machines.