depending on the WU, it's probably about the range of a single 1.6 G5 (not the imac, don't know about that one) or a dual 1.8. Some work units are a lot faster on PCs...some are slightly faster on Macs.
If you have a Pentium and it's got HyperThreading turned on, then one instance of Folding will max out at 50% of your processor usage. If you want to fold as quickly as possible, either turn off HT or run 2 instances of Folding. One easy way to do this is to install 2 copies, one in a folder called FAH and one in a folder called FAH2. If you have multiple logins, you can log in as the "extra" account and start up folding from the FAH2 folder and then switch over to the other user. I believe there are some things set up already online somewhere that will run two instances for you automatically, so you don't have to do this at all...but you can if you need to...it works.
at that point, a HyperThreaded 2.8 will be about the same, maybe slightly slower at times, as a dual 1.8 or dual 2.0 G5.
So pretty good bang for buck.
I have a PC here at work that our accounting person uses...it's 3.0 Ghz with HT turned on, and she gets more points a day from that machine than my dual 1.8 does...hands down.
