CPU: Intel Core 2 Duo P8400 @ 2.26GHz.
I've had this laptop for about 3 years and in the past month I've started getting periodic framerate drops in games. Usually the pattern is random, something like:
4 seconds of 29-31 ms/frame, 9 seconds of 66-68 ms/frame, 60 seconds of 29-31 ms/frame, 3 seconds of 66-68 ms/frame...
I've had this problem both in the game I'm developing (I'm a game programmer) and in OpenArena which I used to test this.
After some musing I think I've found the problem - the CPU is getting throttled, either to save power or to pervent overheating. Core Temp confirms this - it shows the CPU frequency fluctuating between 799MHz and 2260MHz and everything in between, and the low MHz periods coincide with framerate drops. This happens even when both cores have a temperature of 41 celsius, so I don't think it's due to overheating.
I looked for a setting to disable Intel SpeedStep in my BIOS, thinking I can go well enough without it, but there was no such setting in the BIOS (probably because of a custom OEM BIOS). I think this should be doable from my OS (win 7) too - I went to
Control Panel -> Power Options -> High Performance -> Change plan settings -> Change advanced power settings -> Processor power management and set:
minimum processor state for plugged in = 100% maximum processor state for plugged in = 100% cooling policy for plugged in = Active
But there was no effect, even after a reboot.
Interestingly, there are long periods (many hours) in which the problem disappears and the CPU stays at a stable 2260MHz. Then it reappears. :)
So, it's not because of overheating, and it's not because of power saving (as I've told Windows that I'm not trying to save power). Any ideas?
Edit: the laptop is a Fujitsu Siemens Amilo Pi-3525