In case you are available in the market for a brand new PC, you might be almost certainly all too conscious about the massive number of other CPU fashions to be had. In a prior article we coated the diversities between the Haswell-based desktop Intel Core i3, i5, and i7 CPUs, but it surely seems that there are if truth be told two or 3 other product strains inside of each and every of the ones manufacturers. It’s possible you’ll could also be aware of the “K” or “X” strains, however do you know there also are “S”, and “T” strains as smartly? In step with Intel, those letter designators imply:

  • Ok/X – “Unlocked” – the highest-end desktop CPU with overclocking beef up
  • S – “Performance-optimized lifestyle,” decrease efficiency, decrease energy draw.
  • T – “Power-optimized lifestyle,” lowest efficiency, lowest energy draw.
Editor’s Observe:
Matt Bach is the pinnacle of Puget Labs and has been a part of Puget Programs, a boutique builder of gaming and workstation PCs, because the early days. This newsletter used to be firstly revealed at the Puget weblog.

On this article, we wish to duvet the S-series product line particularly for the reason that specs for S-series processors are if truth be told similar to that of same old Intel CPUs. To resolve the good thing about S-series CPUs we will be able to first take a look at the reliable specs variations between a few S-series processors and their same old opposite numbers then transfer directly to our personal checking out and benchmarking to resolve the true efficiency, energy draw, and thermal variations.

Specification Variations

To check the reliable specs between S-series CPUs and their same old opposite numbers we took 4 of the most recent technology Haswell CPUs. There are, after all, extra fashions to be had from Intel, however now we have discovered that the diversities between S-series and their same old opposite numbers to if truth be told be very constant, so it is a just right illustration of the S-series as an entire.

Fundamental CPU Specs i7 4790 i7 4790S i5 4690 i5 4690S
Base Freq. 3.6 GHz 3.2 GHz 3.5 GHz 3.2 GHz
Max Turbo Freq. 4 GHz 4 GHz 3.9 GHz 3.9 GHz
Cores/Threads 4/8 4/8 4/4 4/4
TDP (wattage) 84 W 65 W 84 W 65 W
Good Cache 8 MB 8 MB 6 MB 6 MB
T case 72.72 °C 71.35 °C 72.72 °C 71.35 °C

This is not an entire listing of all of the reliable specs (you’ll be able to view an entire listing at Intel’s Ark web page) but it surely covers lots of the main specs and the entire tactics through which the CPUs formally range. In step with Intel’s reliable specs, there are truly handiest 3 variations between the 2 other style varieties.

First, the S-series CPUs have a far decrease base frequency than the usual CPUs. You possibly can assume this implies that they’re going to at all times be slower, however now we have proven up to now that the bottom frequency is rather of a meaningless specification because of Intel’s Turbo Spice up and Speedstep applied sciences. Those applied sciences imply that an Intel CPU will handiest infrequently function on the marketed base frequency which brings into query whether or not this spec if truth be told has any relating real-world efficiency.

The second one distinction is the decrease TDP wattage at the S-series processors. Once more, it is a deceptive specification since in step with the Intel Ark specification pages, TDP is explained as … the common energy, in watts, the processor dissipates when working at Base Frequency with all cores lively below an Intel-defined, high-complexity workload.

In different phrases, TDP is handiest what the wattage of the CPU is when working on the base frequency, no longer the utmost frequency as decided by means of Turbo Spice up. And because we have now discovered that the bottom frequency is not an excellent indicator of efficiency, because of this TDP could also be a questionable specification. It no doubt signifies that the S-series processors will have to run at a decrease wattage, however except you disable Turbo Spice up it does no longer whatsoever ensure it.

In any case, the closing distinction is the decrease T case temperature at the S-series CPUs. That is associated with Intel’s overheating coverage and principally is the thermal cutoff level the place an Intel CPU will mechanically decrease its working frequency to take a look at to scale back the volume of warmth the CPU is producing. Additional info on that is to be had in our Have an effect on of Temperature on Intel CPU Efficiency article. Realistically, so long as a CPU has good enough cooling this specification will have to by no means have a bearing at the efficiency of the CPU.

To sum up, all of the reliable specs truly let us know is that S-series processors would possibly be somewhat slower and would possibly run somewhat cooler than their same old identical however it’s some distance from conclusive. For that, we will be able to wish to carry out our personal checking out.

Take a look at Setup

Since Intel’s specs don’t seem to be very nice at appearing the true distinction between the S-series and same old CPUs, we made up our minds to match a Core i7 4790 and a Core i7 4790S to resolve the true energy draw, thermal, and function variations between the 2 CPUs. For this checking out, we used the next {hardware}:

Checking out {Hardware}
Motherboard: Asus Z97-A
CPU: Intel Core i7 4790 3.6GHz 84W Quad Core
Intel Core i7 4790S 3.2GHz 65W Quad Core
RAM: 4x Kingston DDR3-1600 8GB
Onerous Power: Samsung 850 Professional 128GB SATA 6Gb/s SSD
OS: Home windows 8.1 Professional 64-bit
PSU: Seasonic X-650 650W
CPU Cooler Cooler Grasp Hyper TX3

All motive force and Home windows updates have been carried out previous to checking out. Coretemp used to be used to file each the CPU temperature and working frequency in conjunction with a “watts up? PRO” energy meter with USB logging to file the gadget energy draw.

Actual international distinction between 4790 and 4790S

Beginning with the total gadget’s energy draw, we discovered that whilst the gadget used to be idle or in sleep mode, the 2 CPUs had nearly an identical energy draw. Whilst working our more than a few benchmarks, alternatively, we began to look a mixture of effects. In each Unigine Heaven 4.0 Professional and Cinebench R15 (unmarried threaded mode) each CPUs had nearly an identical gadget energy draw. Best Prime95, Linpack, and Cinebench R15 (multi threaded mode) resulted within the Core i7 4790S the usage of much less energy. Even then, the adaptation used to be handiest 5-10 watts (or 4-7%) which is some distance lower than the nineteen watt distinction that Intel advertises.

Upper wattage will have to without delay correlate to better temperatures so it isn’t a surprise that this graph is similar to the facility draw graph. The Core i7 4790S runs at roughly the similar temperature because the Core i7 4790 at idle, all over Unigine Heaven, and all over the one threaded portion of Cinebench R15. Truly, the one vital distinction in temperature happened all over Linpack and Cinebench R15 (multi threaded mode) the place the 4790S ran 4.5 ºC and three.75 ºC (or 5% and eight%) cooler respectively.

With the true gadget efficiency effects we begin to see an overly transparent development. Similar to the facility draw and temperature effects, Unigine Heaven and Cinebench R15 (unmarried threaded mode) carry out nearly precisely the similar with each CPUs. Alternatively, Linpack and Cinebench R15 (multi threaded mode) ran about 5% slower with the 4790S in comparison to the 4790.

So, why the massive variance between the other benchmarks? Clearly, a development exists, because the 4790S and 4790 truly handiest confirmed a distinction in energy draw, temperature, and function all over Prime95, Linpack, and Cinebench R15 (multi threaded mode). What we imagine to be taking place is in some ways associated with the bottom frequency specification we discounted all over the ‘Specification Variations’ phase. It seems although a CPU by no means runs at its marketed base frequency, this specification continues to be a hallmark of the way efficient Turbo Spice up could also be relying at the selection of threads an utility can use.

Efficiency according to selection of lively threads

As we identified previous on this article, because of Intel’s Turbo Spice up era an Intel CPU will nearly at all times function above its rated base frequency when put below load. What’s incessantly lost sight of, alternatively, is that the Turbo Spice up frequency at which a CPU runs is dependent upon the selection of cores actively getting used. In truth, the utmost Turbo Spice up frequency Intel lists on their specification sheets handiest applies if the CPU is the usage of only a unmarried core. As increasingly cores are used concurrently, the utmost Turbo Spice up frequency is diminished.

Most likely, the inconsistencies we discovered within the earlier phase are associated with what number of threads each and every benchmark is in a position to make the most of and the way that affected the volume of Turbo Spice up each and every CPU gained. To resolve the true quantity of Turbo Spice up to be had to our take a look at CPUs according to the selection of lively threads we ran Prime95 on each and every CPU with the bechmark restricted to between one and 8 lively threads.

As you’ll be able to see within the above chart, it’s transparent that as extra CPU threads are getting used, the 4790S runs at an increasingly more decrease frequency than the usual 4790. Which means that even supposing the 4790S and 4790 technically have the very same most Turbo Spice up frequency, they’re very other as extra threads are getting used. Relying at the selection of threads, the 4790S is any place from .1 to .2 GHz slower than the 4790. This is not a lot – handiest about 2.5 to five.3% slower – but it surely strains up nearly precisely with what we are saying in our genuine international benchmarks.

S-series processors are meant to be decrease wattage (this is how they’re essentially marketed by means of Intel) so the fairly decrease efficiency is to be anticipated and in many ways is secondary to the facility draw of the S-series CPUs. What we discovered used to be that the 4790S did certainly draw much less energy when 5 to 8 threads have been getting used, however with fewer than 5 threads the 4790S if truth be told pulled extra energy than the usual 4790 by means of a mean of 6%.

We haven’t any reason for why that is, even if it might merely be that we had an strangely scorching working 4790S and an strangely cool working 4790. Both means, our checking out with those pattern CPUs signifies that the 4790S is if truth be told handiest decrease energy when greater than part of the whole CPU threads are below load.


To summarize each our analysis and checking out effects, there are 3 main tactics through which Intel S-series processors range from the usual fashions:

  • Energy Draw: Our checking out between a Core i7 4790S and a Core i7 4790 signifies that S-series processors draw much less energy when greater than part the threads at the CPU are getting used. Then again, our checking out additionally confirmed that the 4790S if truth be told draw fairly extra energy when lower than part threads are getting used.
  • Temperature: Even if the 4790S used extra energy in some packages than the 4790, we did not truly see the 4790S working any warmer than the 4790 in the ones circumstances. When the 4790S does use much less energy, alternatively, we noticed a drop in temperature of as much as about 5 °C. This is not insignificant, however on the identical time isn’t going to be a recreation changer in maximum scenarios.
  • Efficiency: On packages that may handiest make the most of a couple of threads, the S-series CPUs are necessarily an identical in efficiency to their same old opposite numbers. If an utility can use a better selection of CPU threads (or if many packages are working without delay), alternatively, the S-series CPUs may also be up to 5% slower than the usual fashions.

Total, we might say that S-series CPUs can merely be regarded as being fairly slower, fairly cooler, and slightly extra energy environment friendly than their same old opposite numbers. None of it’s by means of very a lot – and in lots of scenarios the 2 fashions are truly an identical – but when you wish to have a gadget that makes use of fairly much less energy in trade for fairly decrease efficiency than the S-series processors could also be price bearing in mind. Something to remember is that S-series CPUs are generally priced precisely the similar as the usual CPUs so except the small energy financial savings is vital you are going to recuperate efficiency to your greenback from the usual fashions.

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