I have the an issue on my Elitebook Core 2 Duo T9600, the scaling stops to work after few seconds of high load and get stuck at 800Mhz.
Temperature is around 50-60°C for both cores, bios_limit is reporting the correct max speed 2534000 (2.53Ghz). The only wrong information I can find is in */sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq* which shows 1520400 rather than 2534000 but anyway, the CPU never goes beyond 800Mhz. It appears either on AC and on battery.
My system: Ubuntu Raring 13.04 Kernel 3.8.0-19-generic x86-64
Is there a way to disable completely the scaling. I don't have any cpu freq manager running in userland.