The webowner may be able to tell, but for now think they list out the 322 thousand machines and what different CPUs/OS they have that were registered for BOINC, with all the known issues of inability to merge devices and duplicate registrations here. Cant remember where I saw the 103.... could have been BOINCsynergy. The number came close to some other back envelope extrapolations I did. WCG knows the number is inflated, but they all did return at least 1 job.

PS the 322k coincides with what i saw at BOINCstats where they also list like 317k active.