A bit of a surprise here - my home PC (see sig for spec details) versus a Dell Inspiron Mini 10v notebook (which has a dual-core Intel Atom N270 1.6GHz), using WinRAR's benchmark tool - the Athlon XP 3200+ only just beats it.
Intel Atom N270: 349KB/sec
Athlon XP 3200+: 351KB/sec
Athlon II X2 240: 1.1MB/sec (DDR3-1333, standard timings - Crucial standard mem dual channel)
Intel Core i7-920: 2.8MB/sec (DDR3-1333, faster timings - Crucial Ballistix mem triple channel)
IIRC, the last two were using the 64-bit version of WinRAR on Win7. The first two are on 32-bit WinXP SP3.
I'll try to remember to take a note of what the Phenom II X4 945 can do when I finish setting it up on-site.
I've got a Core i7-870 which I'm waiting on parts for (another customer build unfortunately - why can't they give me cheques just as a present for me to get a new computer?!?
). Ballistix mem again, dual channel. Should be interesting.