This seems to happen in most every linux distro I try (haven't tried windows yet). I apologize in advance for the nonstandard situation in which it arose, but I will explain that after I explain the fundamental problem:
My CPU (Intel Core 2 Quad Q6600) keeps being throttled. When I boot up some distros which are more verbose during boot, I often see a message telling me that my CPU temperature exceed a threshold, and therefore has been throttled. This really seems improbable to me for a variety of reasons:
The CPU is well-cooled, with two fans blowing directly onto its stock heatsink and one large fan exhausting. The whole system is very clean.
The CPU PWM fan increases to maximum load during boot and during BIOS inspection, so I know that the BIOS seems to think this is a problem as well, but as soon as Ubuntu (or any other distro) boots, the fans die down. Various temperature reading programs in Ubuntu have shown me temps that - even under various benchmark loads which SHOULD be more stressful than Ubuntu's launch - do not exceed the recommended maximum for this CPU, which is something like 75C. They usually stay down in the 60s.
During boot, idle, and benchmarking/burn-in tests, the exhaust fan is still expelling absolutely cool air.
For these and other reasons, I am almost 100% certain the CPU is falling victim to a faulty sensor, is there any way I can disable this safety feature in Ubuntu so that the software does not throttle my CPU?
Further information about my system which may be of note:
The CPU has been BSEL modded to run on a 1333mhz FSB rather than the stock 1066 FSB, resulting in a clock (listed in BIOS) of 3ghz instead of the 2.4ghz stock configuration.
The system is running Ubuntu 15.10 off a liveCD image.