I took a look at Rosetta@home tasks which my 4c/8t Haswell Xeon E3 completed before the sprint, using 50 % CPUs for Rosetta@home, 50 % for desktop duties. My following two findings confirm what I remembered from earlier occasions when I ran Rosetta@home. Sample size: 30 tasks, set to 8 h target runtime.
a) 2 tasks had 7 h runtime, 3 tasks had 4...5 h runtime. Their credits/hour (runtime or CPU time) was in line with the 25 other tasks which met the target runtime of 8 h.
b) Credits/hour per task vary a lot.
minimum ............. 22 credits/h
10th percentile .... 34 credits/h
average ............... 52 credits/h
90th percentile .... 67 credits/h
maximum ............ 84 credits/h
coefficient of variation ... 26 %