I always use BIOS manual settings, I was using AMD Overdrive to show max frequency/to show it's got 4 cores.
I rarely use Overdrive for anything other then monitoring my temps, or for pictures to show description specs.
My temperatures never went above 41c at 3.8 ghz 1.45v running under dual core. Also voltage is what creates the heat, not so much the clock.
Also how accurate is this so called ACPI sensor. I want to know because when I had my processor locked at dual core, the onboard CPU diode reported 41c load, and the ACPI reported about 31c-33c.
I am 100% positive the heat sink is correctly seated, and the thermal compound is correctly spread (TX-2).