Here's something to try: Go into the BIOS and turn off hyperthreading. (Depending on one's BIOS version, this may require a search.)
Another machine I play with has a Core i7-2600K, a legendary chip for overclocking compared to anything that followed. There too, the hyperthreading circuits draw more power and throw more heat than they're worth; one can overclock further with hyperthreading off, to overcome any faint advantage that it might offer.
Turning off hyperthreading on my D54250WYK, I can stay under 70 C core temps in my passive case with no fan, running the two physical cores all out, 24/7. (Add back the fan and temps drop to 50 C.) In the original case, turning off hyperthreading would lead to lower fan speeds for a given task.
More importantly, all of the erratic timings I had been seeing with my parallel benchmark task went away. It takes the same 120 minutes each run (compared to 40 minutes on the overclocked Core i7-2600K). Raising current limits in the BIOS no longer has any effect; with hyperthreading off this computation is not constrained by default BIOS current limits.