Blogs Are low-power desktop CPUs worth buying?

Well if you're comparing something like a P4 to an i7, that's completely false. But for arguments sake, lets say you had an i3 and an i7 of the same generation and same clock rate, and suppose you have the exact same motherboard, PSU, OS, and RAM. The i3 will most likely consume more power in the end than the i7, because there are certain tasks that need to be performed every time a calculation is made and the reduction of transistors per core in the i3 reduces it's effectiveness. I remember reading that some phones include quad cores rather than dual cores intentionally for power saving purposes - the average user has no use for a quad core phone, but if tasks are evenly divided among all cores, the CPU doesn't have to raise its clock rate, which in turn saves power compared to a dual core of the same architecture with one of it's cores nearly maxed out. Think of it like this - suppose there's a 1km trail, and you're on foot. The average person could easily do this by walking and not break a sweat. But if you're hopping on 1 foot the entire way, or, running the entire way, you're going to get tired quicker. However, you'd get tired if you went on all 4s too. Efficiency is a matter of proportionate distribution of work while maintaining a certain pace. From what I've noticed, CPUs lose efficiency once you overclock them beyond a certain point (assuming you keep power management options on).

 

The test I linked prove that the 35W i7-4765T is only 15% slower than the 84W i5-4670K while consuming 42% less (for the whole rig) at full load (64W vs 108W). Ok, it's 4C-8T vs 4C/4T, but it proves that HT is efficient and can increase performances even if your severly lower the wattage and frequencies.

Maybe it's better to have more cores with lower frequencies and voltages, but it really depends on what you do. With single threaded apps, you won't save anything ... but with multi-threaded apps it's a total different story.

 

An important factor is idle power consumption, since it's fair to say that a home PC will spend a fair amount of time idle. A standard TDP processor will probably complete a task & return to idle more quickly than a slower-clocked low TDP processor.

As others have said, by changing power profiles in Windows it's possible to run modern CPUs at low power when extra performance isn't required.