Well, here's a quick benchmark I did tonight on my Athlon XP 2200+ (1.8GHz):
Phil's phrot program:
Actually testing 635481*1048576^20480+1 (20482/49152 limbs)
635481*2^409600+1 [-244748,-353119,372855,204230] is composite LLR64=F4D8A6DFADB
1882C. (e=0.10944 (0.143278~6.95512e-16@1.053) t=2326.28s)
By comparison, using the Seventeen or Bust client, in the past I've tested similar numbers in 1122 seconds:
601467*2^409600+1 is not prime. Res64: C89279AB140D4564
So it's not useful for x86 yet. When Phil gets his PPC code working, maybe some Mac afficionado (sp?) can try it.