@joerg_rw - what is missing in your equation is voltage. So if you undervolt while overclock, thus keeping total energy (i.e. average power multiplied by time) in sane limits (near stock) you are safe. And your explanation may leave someone with the impression that overclocking at 800MHz means locking CPU at that speed - which you perfectly know is not true.

Re great Nokia job - recently i have played a lot with kernel code in both n900 and n950, and TBH I am under impression that Nokia just copy/cat what comes from TI. And what comes from TI is a set of parameters which are safe for TI evaluation boards, thus no clock/voltage optimizations specific to n900 exists in n900 kernel. What I totally agree on is that the job Nokia HW engineers have done to dissipate the heat from the SOC is absolutely great.