4. Two Names For The Same Technology: PowerNow And Cool & Quiet, Continued

In operating systems such as Windows 2000 and older that don't provide native support for PowerNow, the use of a PowerNow utility is necessary to switch between the various operating states.

What stands out is a gaping frequency hole of 800 MHz between the lowest operating point at 800 MHz/1.1 V and the next higher, at 1600 MHz/1.4 V. Then, 200 MHz increments follow the 1600 MHz point. This means that the Mobile Athlon64 only has up to four operating points, called power states (P states). We can only guess why the Mobile Athlon64 has so few different power modes compared to its predecessor, the Mobile Athlon XP. That could be because frequent switches to and from between a maximum of nine intermediary stages is not possible since, according to the operating system's requirements, the frequency that should follow the switch between the various operating points is much higher than the technically feasible frequency for the switch between two separate stages (around 2 kHz). It's also possible that testing revealed that frequent switching does not have a positive effect on battery life.

But perhaps AMD only decided for a lower number of operating states for the Mobile Athlon64 because in the past, as far as we know, BIOS developers have so far failed to get around to programming all the power states for the Mobile Athlon XP.

Of the notebooks we tested, only half could harness the CPU's technically possible performance levels.

Yet there is a difference between PowerNow and Cool&Quiet. According to AMD's specifications, the CPU in the desktop PC initially boots up, as dictated by Cool&Quiet, in the maximum P state, i.e. operation is at the highest possible core clock speed. The Mobile CPU in the notebook, on the other hand, boots up at the lowest core speed (800 MHz).

In comparing the Pentium 4-M or the Pentium-M to the Mobile Athlon64, the Pentium 4-M, like AMD's Mobile Athlon64, is found in notebooks in the desktop-replacement/full-size class. The 1.7 GHz Pentium-M's forté is its L2 cache, also with 1 MB, and a similarly high clock speed, compared to the 1.8 GHz Mobile Athlon64 3000+. We opted to compare it to the Pentium-M.