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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  • patrickjchase - Friday, December 12, 2014 - link

    I used to work on SoCs in process nodes down to 28 nm, and the variation from the fast/fast (low-delay, leaky) to the slow/slow (high-delay, low-leakage) corners in modern processes is substantial. The fact that a given vendor isn't binning simply means that they're adding a fair bit of margin.

    For that matter I wouldn't be so sure that Apple doesn't bin. For example it's possible that the A7s in iPhone 5s and iPad Air were binned differently.

    Finally, Intel's volumes create additional binning opportunities. A process condition that happens, say, 0.1% of time time would constitute such as small volume as to be useless to most vendors but adds up to a nice niche for Intel.
    Reply
  • aj654987 - Friday, May 15, 2015 - link

    I think its reasonable to believe they are binned. From a business perspective, is it really necessary to have THAT many different CPU models that Intel has? At some point you can have too many products and theyre competing with each other. Look at GM and how they had too many brands and rebadged vehicles that are competing with each other. I dont think there IS any business advantage to artificially create as many different chip models as intel has, though there is a business advantage to being able to salvage chips they would otherwise have to toss.

    When comparing to ARM processors, those are less complex and less expensive. If they have an ARM chip that tests bad, it may make more sense to toss it then to cripple it and sell it as a lower model. Also like consoles there is a preference to have the same speed across all devices, where as with a PC, different CPU speeds seem more acceptable to the market.
    Reply
  • eanazag - Thursday, December 11, 2014 - link

    The 65W parts seemed to show increased performance in IGP gaming versus their non-S counterparts. 4790S vs 4790. I would suspect the TDP budget for the IGP is unaffected by the TDP reduction and therefore might get a little thermal room to run harder. Looking at Intel ARK the 4790 series all runs at 350 base and 1.2 max; the 4790K is able to boost higher to 1.25GHz. The IGP gaming number seem to tell this story.

    You can also see when a discrete GPU is thrown in there the non-S parts then perform above the S parts in gaming.

    For IGP gaming AMD is still the best choice; and that is about all they're good for.
    Reply
  • evilspoons - Friday, December 12, 2014 - link

    This is the story in thermally-limited situations like the Surface Pro 3. The i5 model is faster at games than the i7 simply because the i5's CPU uses less of the thermal budget so the iGPU can stay faster for longer. In a more extreme case, running old non-CPU bound games (World of Warcraft), the i3 model is even better - the CPU leaves even more room for the iGPU.

    Of course, this could all be avoided by the game simply going "hmm, which one is really slowing me down - the CPU loop or the GPU loop?" and then throttling one to match, but the odds of that happening any time soon are pretty poor.
    Reply
  • mortenelkjaer - Friday, December 12, 2014 - link

    IGP gaming, What is that? Reply
  • MrSpadge - Thursday, December 11, 2014 - link

    No. The regular Intel 22 nm CPUs are so good that they can run ~4.0 GHz at ~1.0 V, whereas stock gives them almost 1.2 V at the top turbo bin. So cutting down on power consumption hardly requires any effort. Reply
  • Samus - Thursday, December 11, 2014 - link

    Eventually wear and leakage will cause tapering. The long-term reliability is Intel's goal which is why these chips are so conservatively clocked. I've already read reports of people running Haswell at 1.3V that initially had them stable at 4.6+GHz and a year later, can't crack 4.2GHz at 1.2V.

    Keeping these things around 1.0V is key to their service life. As Spadge said, try to get the most you can out of the stock voltage (usually 4GHz, sometimes more.)
    Reply
  • B3an - Thursday, December 11, 2014 - link

    Completely off topic, but you guys do an article on AMD's new "Omega" driver? It has loads of new features and i can't find anywhere that's done a proper in-depth article on it. Reply
  • DiHydro - Thursday, December 11, 2014 - link

    The Tech Report, and PCPer both have articles about the features and performance gains of the Omega driver release. Reply
  • JarredWalton - Thursday, December 11, 2014 - link

    It's in the works. Ryan and I both were out for a few days due to illness, unfortunately. Reply

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