More than half of all desktop processors on Sandy Bridge microarchitecture boast lower power consumption. However, so far we haven’t seen any real benefit in such a strong focus from Intel on energy-efficient models.
Of course, we won’t deny that Core i5-2400S processor we tested today consumes less power than standard CPUs with 95 W TDP. And it has every chance to win those users who care a lot about saving energy and lowering system noise. Especially, since it is only $11 more expensive than the regular CPU.
However, if you decide to go with Core i5-2400S or any other similar processor from the S-series, you should keep in mind a few things. Most importantly, Intel doesn’t preselect better semiconductor dies for their energy-efficient models, but simply lowers the clock speeds, as simple as that. As a result, Core i5-2400S runs slower than the regular Core i5-2400, and sometimes this difference is substantial and can reach up to 20% under heavy load. However, the energy savings in this case are not that noticeable. Theoretically, the TDP difference between energy-efficient and regular processors is 30 W, but in reality we saw only 12 W at the most in a very limited number of usage scenarios. Moreover, there is simply no difference of any kind during HD video playback or 3D graphics processing.
Frankly speaking, Core i5-2400S not only performs worse than Core i5-2400, but also can’t boast the best performance-per-watt ratio, which is pretty strange for an energy-efficient model. On the other hand, even regular Sandy Bridge processors do not consume that much power to begin with and may suit perfectly fine for small and quiet systems. So, solutions like Core i5-2400S are mostly niche products rather than an appealing option for home and HTPC systems, because you can always go with a faster and cheaper Core i5-2300 instead of Core i5-2400S without any harm to the system power consumption.
In conclusion I would like to stress that you shouldn’t base your choice of an energy-efficient processor on its model number. As we have seen today, Core i5-2400S works slower that Core i5-2300, which means that Intel uses a different base for their S-series numbering. Obviously, T-series processors are marked using the whole different algorithm, so looks like the formerly crystal-clear model numbers hierarchy has been seriously disturbed, and definitely not in users’ favor.