According to our test data, the S and T series processors are inferior to their ordinary counterparts in terms of computing performance. This is the tradeoff for their lower power consumption which is achieved by means of lower clock rates. However, we've been talking about the power savings theoretically, using data from the official specs. Now we want to check out how economical these CPUs are in practice.
The graphs below (unless specified otherwise) show the full power draw of the computer (without the monitor) from the wall socket. It is the total power consumption of all system components. The PSU's efficiency is taken into account but our Corsair AX760i is a highly efficient 80 PLUS Platinum product, so its effect on the result is very small. We enable Turbo technology and all power-saving technologies: C1E, C6 and Enhanced Intel SpeedStep.
First we test our PC configurations in idle mode.
All of the processors have the same results here. Irrespective of its specified TDP, a Haswell-based CPU switches into a power-saving state when idle, minimizing its power consumption to zero. So the numbers in the diagram are rather indicative of the power draw of the rest of the configuration.
Next we measure the peak power consumption when our configurations run the 64-bit version of the LinX 0.6.5 utility (based on the Linpack suite) with support for the AVX2 instruction set.
It is in this test that we can estimate the real power requirements of Intel’s CPUs. According to the numbers, the 65-watt Core i5-4670S is not much more economical than the regular Core i5-4670. Moreover, it is even worse in real power consumption than the Core i5-4460 which is specified to have a TDP of 84 watts. As for the 45-watt Core i5-4670T, it is more economical than any other quad-core CPU but needs more power than the dual-core i3-4360 which is supposed to consume up to 54 watts.
The Linpack-based LinX utility makes the processor consume much more power than at average real-life loads, so we will have a more realistic test as well. We will transcode a video clip using the 64-bit x264 codec version r2431.
We have the same standings as in the LinX test above with only one exception: the 54-watt dual-core i3-4360 consumes more power than the 45-watt quad-core i5-4670T. In other words, the CPUs have exactly the same standings at real-life loads as they should have according to their official specs.
Now let’s see what we have in graphics-heavy applications. We'll run the Furmark 1.13.0 utility to load the processors' integrated graphics cores.
Considering that the graphics cores of the tested CPUs have comparable specs, it is no wonder that they have similar power requirements at 3D load. The higher energy efficiency of the Core i5-4670S and Core i5-4670T models doesn't show up here at all.
We must note, however, that the previous diagram describes the case of a heavy graphics core load combined with a low CPU load. In real-life applications the overall load is going to be distributed between a processor's GPU and CPU parts. We'll run World of Tanks as an example of such an application.
Oddly enough, the processors do not differ much in power consumption when running games. It is the integrated graphics core which has to deal with the bulk of the overall load after all, and it is the same in the energy-efficient processors as in the regular ones. That's why the difference between the Core i5-4670 and Core i5-4670T is a mere 10 watts whereas the 84-watt Core i-4460 with a slower graphics core needs less power than the 45-watt T series model. Thus, the energy efficiency of Intel’s specialized processors shows up at computing loads only. You must take this fact into account in order not to have excessive expectations about the Core i5-4670S, Core i5-4670T and other products of this kind.