Yousef, Re: " If you get the higher frequency by increassing the current in the transistors (Idsat), then the power goes up as the square of frequency."
You say,
No John ... to increase the Idsat, you must either physically change the FET (shorter Leff, Gate thickness, Source/Drain resistance ...) or increase the voltage.
If you follow this thread back to where it started, increasing Vcc is exactly what I was talking about -- the K6 desktop CPU will run at a higher Vcc than the notebook CPU (in 0.25 um), therefore it will have a higher Idsat, higher operating frequency and power dissipation proportional to the square of the voltage ratio. For a particular CPU, the only thing you can play with to get a higher operating frequency is the Vcc (core voltage). This was confirmed by me recently for a K6-166 which operated flawlessly at 188 MHz at Vcc=spec level=2.9v, could do 200 and 208 MHz at 3.2v and 225 MHz at 3.3v. Similarly, its a sure bet that if K6 (0.25u process) notebook chips do 300 MHz at 1.8v, they'll do 350MHz at 2.1v. (K6-3D will go beyond that).
AMD's 0.25 generation has apparently physically shrunk the FET by more than the expected (0.25/0.35)^2 ratio, judging by the die size. This is why I believe AMD will catch up to Intel on CPU speed instead of being 2 speed grades behind.
Petz |
