Starting temperature? Do you mean where to anchor the fan speed control curve? My philosophy is that the earlier you begin applying a response (i.e. increase in fan speed duty cycle) to temperature increase, the lower will be the average temperature over the higher usage periods and the less noticeable the fan/blower/pump response necessary to account for incremental temperature changes. The goal is simply to keep the temperature below the processor's Tjmax (Maximum Junction Temperature). From some minimum duty cycle, linearly increase the duty cycle such that 100% is reached some small distance below the processor's Tjmax (which is somewhere in the vicinity of 100c). For example, you could use:
- Minimum Temperature = 60c
- Minimum Duty Cycle = 30%
- Duty cycle Increment = 2%
This would increase the duty cycle from 30% to 100% over temperature range 60 to 95c.
Now, I will give you two answers to the second question. Intel's answer will be that as long as you keep the temperature at or below the processor's Tjmax, your processor will suffer no thermal degradation and should reach its warranted lifetime without issue. I don't like that answer. It is my opinion that it is not good for the processor to spend any significant amount of time at or near its Tjmax. I thus recommend to anchor the top of the response curve some distance - say 5 degrees - below the processor's Tjmax. Remember two things, (1) the heat being generated has to be dissipated and if it cannot be dissipated effectively, it is also going to affect the other circuitry around it - circuitry that is typically not able to withstand temperatures this high for any sustained period - and (2) if the temperature is at or above the processor's Tjmax, the processor is going to be throttling performance to help lower the temperature. If this happens too much, it results in an overall loss of performance. That's a waste. You are playing this off against fan/blower/pump noise, of course.
Aside (up on my soapbox): Laptop manufacturers will often under-design their cooling solution (pocketing the money saved) and rely on the processor throttling itself to protect it from damage. Worse, to make their battery life look better, they will rely on throttling to limit power utilization and extend the available battery power. How slimy! These manufacturers should be sued for selling systems configured like this (ok, off my soapbox now).
Hope this helps,
...S
