3. Special Features Of The Celeron M Compared To The Pentium M, Continued

Moreover, the Celeron M has neither energy saving technology, such as Enhanced Speedstep , nor does it utilize the power mode called "Deeper Sleep". The lack of these energy saving functions causes the Celeron M to lose face somewhat compared to the Pentium M, with regard to its ability to saving energy. The Celeron consumer up to 25 watts, depending on the workload. On the other hand, thanks to Speedstep, the Pentium M might be able to reduce its power consumption under a low processor workload to six watts. Even at a maximum processor workload, the Pentium M's power requirements are more than 10%less than the Celeron M's requirements.

Diagram of the different power modes of a Pentium M CPU

If the CPUs aren't being utilized, then, within fractions of a second, they fall into different sleep modes step-by-step, such as Sleep Mode or Deep Sleep Mode. In these power modes, the Celeron M loses ground with regard to power consumption, which is up to 30% higher than the Pentium M. The cause of this is apparently the higher leakage current of the Celeron M's core. Even with the L2 cache that is half the size, and its "intelligent" circuit, the Celeron M can't make any headway. This is because the eight-fold associative L2 cache is subdivided into four quadrants per path, and consequently 16 segments of 32 kB each. However, for both processors, the cache logic makes sure that during an access, only the segment being addressed is active (32 kBytes). The rest of the cache remains inactive. The power consumption of an L2 cache configured that way is therefore almost independent of the total size of the cache. In a Pentium M, the L2 cache is comprised of 32 segments with a size of 32K Bytes each.

Also, the Pentium M can score more points against the Celeron M, since in Deeper Sleep Mode, which the Celeron M can't manage, its power consumption is less than one watt.