Replies to post #67214 on Advanced Micro Devices Inc (AMD)

[alan81]

TDP does not drive battery life,
Typical power does.
A 49C Opteron 170 uses less than 28W TDPmax. You could put that into a laptop and have good battery life.
The problem here is that you could not put that into a laptop with a 49C case temperature. The typical 28W laptop CPU will have a Tcase of 100C. Assuming an Ambient of 42C (the AMD number), the 49C Tcase part would need a heatsink almost 8 times larger than a 100C Tcase part.
In addition, it seems to be a common error to equate TDP to battery life. Typical power is a much better indicator of battery life than TDP. I think many believe TDP and typical power are related, and certainly they are... but that relationship is loose at best. For example, the Pentium-M has a TDP of around 25W and a typical of around 1W for a ratio of 25 to 1. OTOH, the P4 has a TDP of around 100W and a typical of what? 25W? Maybe 50W for a ratio of between 2 to 1 and 4 to 1.
Smaller TDP is important to keep the laptop thin and light.
Smaller typical power is important for long battery life.
--Alan