I noticed my Xeon E5-1620 runs better with -4, -s 600000 and -d 16 vs -t 8 -s 2000000 or 1500000 and -d 8.
Can it be that Hyper threading hurts mining performance?
My i7-2700K runs better with -t 4 than -t 8. Thermal throttling at t8 forces it to downclock for one, the PPS remains nearly the same.