OK - How's this for dealing with multiprocessors...
Hosts with two or more processors are permitted, but will have a handicap applied to their outputs. This will be applied by multiplying the reported credit by a handicap factor once for each reported CPU. The handicap will be: 0.89 for Xeon systems showing more than 2 CPUs with speed of 2.0GHz or more, 1.00 for Pentium 4 systems showing up to 2 CPUs, 0.71 for Opteron-based systems, and 0.85 in all other cases.
Just to show how this works, let's take a Dual Opteron, Dual Athlon MP, and Dual Xeon HT, all with 1,000 credit:
Opteron: 1000 * 0.71 * 0.71 = 504.1
Xeon: 1000 * 0.89 * 0.89 * 0.89 * 0.89 = 627.4
Athlon MP: 1000 * 0.85 * 0.85 = 722.5
Single CPU: 1000 (no handicap)
The weightings may still need a bit more tweaking, so I'm open to suggestions on those. The Xeon weightings are intended for the Nocoma core. I can't tell the difference between, for example, Nocoma and Prestonia, so older Xeons will be at a disadvantage.
The other alternative is to keep the multiprocessors completely separate.