Despite being an integral part of Intel's product stack, reviews of the lower power models are few and far between. For those of us that have no interest in overclocking, the lower power parts can offer similar stock performance to the big boys but at 65W and 35W. Today we are testing three chips available from Newegg at $135, $215 and $315.

Not All CPUs are Alike

While Intel's CPU naming scheme is finally starting to make sense to home system builders, their product stack consists mainly of generic numbers in either Celeron, Pentium, i3, i5 or i7 format unless someone sits down and explains the trend to the individual. These models are clearly defined whereby a bigger number tends to mean more frequency. With this general stack of names, there are sometimes models that come with extra letters. Overclockers already know the K and the X models as having their multiplier unlocked for extra potential, but for other CPUs we have T and S destinations. (Xeons also use the letter L, and mobile chips have H/Y/U.)

Simply put, T is used for 35W/45W models and S is for 65W models. The S models tend to have similar single core performance to their normal cousins, but reach 65W by reducing the multicore frequency when the CPU is loaded. The T models reduce both single core and multicore frequency to hit their 35W or 45W, but tend to be a little more esoteric in their position in the stack.

In general there are two ways to reduce the TDP on a CPU. We can either reduce frequency (easy) or reduce voltage (difficult). Reducing the voltage results in more of a change in power consumption, but the best way to tackle this is when Intel performs its binning process.

When a manufacturer creates a wafer of CPUs, these have to be tested for accuracy of calculations, functions, and the voltage/frequency response. It is this latter characteristic which matters most when determining what product in the stack it should be. The units with the highest frequency for the lowest voltage (on a scale) tend to be reserved for the fastest processors or Xeons. Note that it is not only a single data point being tested, but a whole scale from low frequency to high frequency. The unit has to match an entire line to be sufficient for that designation. Where the low power CPUs come in is that they follow a particular line at a potentially lower voltage range than expected.

There have been reports of the regular branding of CPUs being reduced in frequency and matching the stability of the S/T processors. That is entirely possible, as a unit can be a member of many bins at the same time. At the end of the day, when you purchase a lower power processor, you are essentially guaranteed that level of performance and TDP by the processor manufacturer.

The Product Stack

To represent Intel's Haswell line-up, I want single out where the S and T processors stack up against their normal counterparts. Thus is made somewhat difficult by the Haswell refresh earlier this year which caused a frequency bump in most models, but both pre-refresh and post-refresh processors are still up for sale in most markets.

Intel Haswell T CPUs
  Cores / Threads TDP L3 Base
Frequency
Turbo
Frequency
OEM Price
i3-4130T 2 / 4 35W 3MB 2900   $122
i3-4150T 2 / 4 35W 3MB 3000   $117
i3-4160T 2 / 4 35W 3MB 3100   $117
i3-4330T 2 / 4 35W 4MB 3000   $138
i3-4350T 2 / 4 35W 4MB 3100   $138
i3-4360T 2 / 4 35W 4MB 3200   $138
i5-4460T 4 / 4 35W 6MB 1900 2700 $182
i5-4570T 2 / 4 35W 4MB 2900 3600 $192
i5-4590T 4 / 4 35W 6MB 2000 3000 $192
i5-4670T 4 / 4 45W 6MB 2300 3300 $213
i5-4690T 4 / 4 45W 6MB 2500 3500 $213
i7-4765T 4 / 8 35W 8MB 2000 3000 $303
i7-4770T 4 / 8 45W 8MB 2500 3700 $303
i7-4785T 4 / 8 35W 8MB 2200 3200 $303
i7-4790T 4 / 8 45W 8MB 2700 3900 $303

 

Intel Haswell S CPUs
  Cores / Threads TDP L3 Base
Frequency
Turbo
Frequency
OEM Price
i5-4430S 4 / 4 65W 6MB 2700 3200 $182
i5-4460S 4 / 4 65W 6MB 2900 3400 $182
i5-4570S 4 / 4 65W 6MB 2900 3600 $192
i5-4590S 4 / 4 65W 6MB 3000 3700 $192
i5-4670S 4 / 4 65W 6MB 3100 3800 $213
i5-4690S 4 / 4 65W 6MB 3200 3900 $213
i7-4770S 4 / 8 65W 8MB 3100 3900 $303
i7-4790S 4 / 8 65W 8MB 3200 4000 $303

If we do direct comparison with a few of the S processors with their non-S counterparts, we see their main difference is just the multicore frequency to drive the TDP down.

Intel Haswell S CPU Comparison
  Cores / Threads TDP L3 Base
Frequency
Turbo
Frequency
OEM Price
i5-4590S 4 / 4 65W 6MB 3000 3700 $192
i5-4590 4 / 4 84W 6MB 3300 3700 $192
i7-4770S 4 / 8 65W 8MB 3100 3900 $303
i7-4770 4 / 8 84W 8MB 3400 3900 $303

With the T processors, we see a more aggressive trend especially with the i7 range.

Intel Haswell T CPU Comparison
  Cores / Threads TDP L3 Base
Frequency
Turbo
Frequency
OEM Price
i3-4160T 2 / 4 35W 3MB 3100   $117
i3-4160 2 / 4 54W 3MB 3600   $117
i7-4770T 4 / 8 45W 8MB 2500 3700 $303
i7-4770 4 / 8 84W 8MB 3400 3900 $303

The i7 35W processors have always been a fascination of mine (much like the 65W 12-core Xeon we reviewed earlier in the year). Ultimately these are best for work flow that can use multicore processing but the code has significant memory delays. This reduces the idle time per core and uses less power.

The purpose of this review is to see how these processors compare to those we have already tested. We currently have a good spread of the Haswell range, and all the results can be found in our online benchmark comparison database, Bench.

Test Setup

Test Setup
Processor
Intel Core i3-4130T 35W 2C/4T 2.9 GHz
Intel Core i5-4570S 65W 4C/4T 2.0 GHz / 3.0 GHz
Intel Core i7-4790S 65W 4C/8T 2.7 GHz / 3.7 GHz
Motherboards ASUS Z97 Pro
MSI B85M Eco
Cooling Cooler Master Nepton 140XL
Power Supply OCZ 1250W Gold ZX Series
Memory G.Skill RipjawsZ 4x4 GB DDR3-1600 9-11-9 Kit
Memory Settings 1600 9-11-9-27 1T tRFC 240
Video Cards MSI GTX 770 Lightning 2GB (1150/1202 Boost)
Video Drivers NVIDIA Drivers 337
Hard Drive OCZ Vertex 3 256GB
Optical Drive LG GH22NS50
Case Open Test Bed
Operating System Windows 7 64-bit SP1

Load Delta Power Consumption

Power consumption was tested on the system while in a single MSI GTX 770 Lightning GPU configuration with a wall meter connected to the OCZ 1250W power supply. This power supply is Gold rated, and as I am in the UK on a 230-240 V supply, leads to ~75% efficiency > 50W, and 90%+ efficiency at 250W, suitable for both idle and multi-GPU loading. This method of power reading allows us to compare the power management of the UEFI and the board to supply components with power under load, and includes typical PSU losses due to efficiency.

We take the power delta difference between idle and load as our tested value, giving an indication of the power increase from the CPU when placed under stress.

Power Consumption Delta: Idle to AVX

Power consumption for our i3 and i5 samples were near on the mark, whereas the i7-4790S scored 102W from idle to AVX. This is more than the i7-4770K, which might come across as a bit alarming.

We also have some full system power draw numbers from the MSI B85M ECO review, while using a Rosewill Silent Night 500W Platinum power supply. These are still in the 5% power used range for the unit, so efficiency is still around 70-80%.

Power Consumption w/Integrated Graphics

Load Delta Temperature on Intel Stock Cooler

At request from some of our readers on Twitter, we also measured the temperature delta from idle to load on the stock Intel cooler.

Temperature Delta: Idle to AVX

CPU and Web Performance
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  • nathanddrews - Thursday, December 11, 2014 - link

    Hmph. Reply
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  • Khenglish - Thursday, December 11, 2014 - link

    So you think these CPUs really are better binned? An undervolted K series cannot always pull off the voltages at the same clocks as a S series?

    If so do you think these better binned chips finally at least match Ivy Bridge in terms of performance per watt?
    Reply
  • casteve - Thursday, December 11, 2014 - link

    No, they aren't better binned. Another site looked at the voltage vs. freq curve and found that the std TDP, S, and T parts all followed the same curve. That i7 S part looks like an oddball. Reply
  • Samus - Thursday, December 11, 2014 - link

    I work with HP Elitedesk 800's all the time with I5-4570S CPU's. They're incredibly small and quiet, much more so than the identically sized USFF dc7900 Core 2 Duo's they replaced. Reply
  • name99 - Thursday, December 11, 2014 - link

    We constantly hear about how aggressively Intel bins parts, how each model is a special snowflake that's exactly optimized for its role, etc etc. I've yet to see any evidence that this is actually true (as opposed to "Intel engages in very aggressive market segmentation --- by product name".

    The primary reason I'm not convinced is that no-one else bins nearly as aggressively. Apple, never a company to miss the opportunity for a dollar, doesn't engage in some obvious binning (eg ship the iPhone6+ at 100MHz faster; or even give you a 100MHz speed boost in each model as you go from 16GB to 32GB to 64GB storage). Qualcomm offers a fairly limited palette of Snapdragon speeds. Samsung, the master if there ever was one, at slicing and dicing phone models, doesn't offer the same phone at speeds of 1, 1.5, and 2GHz; etc etc.

    We have to assume that
    - everyone else's processes are crazy uniform compared to Intel OR
    - Intel is MUCH smarter than anyone in how they are able to bin OR
    - binning (at the micro segmentation Intel offers) just is not a real thing
    and the third option seems the most plausible to me.
    Reply
  • Samus - Thursday, December 11, 2014 - link

    Almost nobody pays attention to GHz numbers in mobile devices. Nobody really cares. And the scaling with ARM really means nothing. Apple consistently has among the highest performance ARM CPU's yet they're lower clocked and lower core count than everyone else. Binning ARM CPU's would require two things in order to be profitable: real-world benefits to a slightly higher clock speed, and marketing the higher clock speed as worth the premium. Currently there are neither. I'd guess 99/100 people don't even know the clock speed of the phone they own, because that's how irrelevant it is. For many applications (such as gaming, where performance is not consistent across the majority of devices) the GPU matters more than the CPU because of how heavily optimized these apps are for the GPU.

    The PC landscape is totally different.. You still have PC's sold that have 1/10th the performance of a Core i7.

    Now, where your idea could be interesting is if they sell an "eco" chip that runs at a lower voltage due to binning. People MIGHT be willing to pay extra for a phone with +20% battery life.
    Reply
  • Kjella - Friday, December 12, 2014 - link

    Or perhaps the simplest and most obvious explanation - Apple feels they're more in the console game than the PC game. Offer one consistent level of performance across all iPhones of the same generation and that's the spec all developers need to relate to. Reply
  • Hrel - Friday, December 12, 2014 - link

    - everyone else's processes are crazy uniform compared to Intel OR
    - Intel is MUCH smarter than anyone in how they are able to bin OR

    Those are both true.
    Reply
  • wumpus - Friday, December 12, 2014 - link

    So Intel chips can't be overclocked and produce more watts than different lettered processors under identical conditions? That isn't what was tested and would be a rather shocking development.

    Chips take a considerable time to fab. Markets change fast and somehow Intel manages to produce what the market needs in the face on negligible competition? Yea, I really believe that they are really binning and not simply segementing to what marketing wants.
    Reply

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