Intel Core i5-655K & Core i7-875K Unlocked Processors Review

[Patrick (MAC) MacMillan]

If you follow computer tech news with any vigilance you have undoubtedly already heard that Intel was planning to release a few multiplier unlocked processors, and that's what we have the privilege of showing you today in the form of two LGA1156 models: the Core i5-655K and Core i7-875K.

The Core i5 K model is a unlocked variant of the current Core i5-650, a 3.2Ghz dual-core/quad-thread processor that is based on the Clarkdale 32nm microarchitecture, and thus also features an integrated GPU. The Core i7 K model is a Lynnfield-based chip, and it is an unlocked version of the range-topping Core i7-870, a 2.93Ghz quad-core/eight-thread processor which can Turbo Boost up to 3.6Ghz. These processors not only feature unlocked CPU multipliers, but have fully selectable DDR3 ratios as well as adjustable power/current limits. Now you might expect these unlocked models to carry a hefty premium, but as you will see in the following pages, not so much...

It seems Intel is slowly getting more amenable to catering processors to the enthusiast segment without having to completely rape their wallets (*cough* Extreme Edition *cough*). Now this is not the first time that Intel have released an unlocked non-Extreme Edition processor. Last August, they unveiled the Pentium Dual-Core E6500K, a 2.93Ghz dual-core CPU based on the Wolfdale-3M architecture. Being a lower-end model with less cache than the fully-fledged Core 2 Duo E8000 series it didn't exactly get enthusiast tongues wagging, especially since it was exclusive to the Chinese market...unless you were willing buy one at a healthy premium from an eBay reseller. Thankfully, these new Intel K-series models, which will officially launch at Computex next week, will be available worldwide so consumers won't have to jump through any hoops to finally get their hands on multiplier-unlocked processors from Intel.

In this review, we not only put these two new chips through our usual benchmarking process, but also handed them off to our world-class overclocker 3oh6, who tested how our two samples fared under air cooling, phase change, and liquid nitrogen (LN2).

 

[MAC]

Intel Core i5-655K

Intel Core i5-655K

Click on image to enlarge​

As you can see from this slim box, the rumours that Intel would bundle a variant of the DXB-B cooler, that was launched with the Core i7-980X, with these K-series processors is false. We have no problems with this omission since enthusiasts should be absolutely be using third-party cooling solutions, especially with processors designed for overclocking.

As is visible on the box, these K-series processors do also come with a 3-year warranty. Therefore, we can assume that Intel is OK with consumers overclocking these particular models. That should please the worriers who don't overclock merely due to a fear of voiding their warranty.

Now the Core i5-655K obviously falls within the Core i5-600 series 'Clarkdale' LGA1156 family, but just
in case you aren't familiar with Intel's naming scheme here is a recap: Intel have chosen their Core i3/5/7 brands to help highlight the number of threads and specific technologies that each processors series supports. Simply put, Core i7 models are eight-thread processors which feature both Hyper-Threading (HT) and Turbo Boost technology. The Core i5 models are four-thread processors with Turbo Boost. The Core i5 series will now be particularly confusing to consumers though, since it is comprised of the 4-core/4-thread i5-700 series and the brand new 2-core/4-thread i5-600 series. Then we have the Core i3-500 series models, which are 2-core/4-thread processors but without Turbo Boost. Lastly, we have Pentium G6000 series, which will be dual-core processors without Turbo Boost or Hyper-Threading.

It is quite a mishmash, but thankfully we are only interested in the Core i5-600 series models on this page. The tables below should help provide greater insight about the various Core i5-600 'Clarkdale' variants.

As you can see, the Core i5-655K is effectively identical to the Core i5-650. They both have exactly the same specifications in every respect, except for the obvious fact that the Core i5-655K has unlocked multipliers. The K-series chip also carries a not insignificant $40 price premium. Whether unlocked multipliers are worth the $40 really depends on whether you are a 'set it & forget it' overclocker, or someone who enjoy's tweaking all the time. The price increase is not that bad though since at $216 Intel are knowingly decimating the potential sales of the $284 i5-670.

Click on image to enlarge​

There's nothing particularly unique about the exterior of the new Core i5-655K, it is identical to every other LGA1156 processor on the market. Obviously our chip is an engineering sample, but otherwise what you see is what you get.

For those of you who are interested, our particular sample was manufactured in the 4th week of 2010.

Click on image to enlarge​

The connoisseurs among you should already have noticed that the Core i5-655K features a brand new core revision. While current Clarkdale processors are all based on the C2 revision, this new chip features the updated K0 revision. Normally this would indicate eight respins, but that doesn't seem likely (or necessary) in this case since there was nothing actually wrong with Clarkdale's core, as far as we know. Obviously we are all hoping for improved overclocking headroom, and we will find that out in the coming pages.

If you aren't familiar with the particulars of the Clarkdale microarchitecture, want to know more about the various models, or perhaps the integrated GPU, we highly recommend that you take a peak at our original Clarkdale review article. It should answer any and all questions.

Now let’s take a look at the second K-series processor that Intel is launching at Computex next week, the very interesting Core i5-875K.

 

[MAC]

Intel Core i7-875K

Intel Core i7-875K

Click on image to enlarge​

The Core i7-875K has the same slim box as the i5-655K, although with different branding. It also doesn't come bundled with a variant of the DXB-B cooler, that was launched with the Core i7-980X. Again that is a good thing since enthusiasts should be be using third-party cooling solutions, especially with processors designed for overclocking.

As stated before, these K-series processors do also come with a 3-year warranty. Therefore, we can assume that Intel is OK with consumers overclocking these particular models. That should please the worriers who don't overclock merely due to a fear of voiding their warranty.

The Core i7-875K is a Lynnfield-based LGA1156 processor. For those of you who are confused with Intel's LGA1156 lineup, which is understandable since it mixes both Clarkdale and Lynnfield models, here is a recap: Intel have chosen their Core i3/5/7 naming scheme to help highlight the number of threads and specific technologies that each processors series supports. Simply put, Core i7 models are eight-thread processors which feature both Hyper-Threading (HT) and Turbo Boost technology. Keep in mind that Core i7 processors come in both LGA1156 and LGA1366 form factors, with the Core i7-900 series being the LGA1366 compatible chips. The Core i5 models are four-thread processors with Turbo Boost. The Core i5 series will now be particularly confusing to consumers though, since it is comprised of the 4-core/4-thread i5-700 series and the brand new 2-core/4-thread i5-600 series. Then we have the Core i3-500 series models, which are 2-core/4-thread processors but without Turbo Boost. Lastly, we have Pentium G6000 series, which will be dual-core processors without Turbo Boost or Hyper-Threading.

Naturally, we want to compare the Core i7-875K with the other Lynnfield-based chips, which means the i5-750 and the other i7-800 series models. The tables below should help provide greater insight about the current Lynnfield variants.

Specifications-wise, the new i7-875K is 100% identical to the current flagship i7-870, but obviously it comes with unlocked multipliers. Perhaps more importantly though, the i7-875K comes with an extremely unexpected $220 price cut...for now. Intel have indicated that this price point might not last forever, so take advantage of it while you can.

Click on image to enlarge​

As with the Core i5-655K, there is nothing particularly unique about the exterior of the i7-875K, it is identical to every other LGA1156 processor on the market. Obviously our chip is an engineering sample, but otherwise what you see is what you get.

For those of you who are interested, our particular sample was manufactured in the 49th week of 2009.

Click on image to enlarge​

Unlike the Core i5-655K which features a new core revision, the i7-875K features the same B1 revision core as every other Lynnfield-based processor.

If you want to know more about the Lynnfield microarchitecture, we recommend that you read our original Lynnfield review article. It contains a wealth of information about the Core i5-700 and i7-800 series processors.

Now it's time for some benchmarks!

 

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Test Setups & Methodology

Test Setups & Methodology

For this review, we have prepared four different test setups, representing all the popular platforms at the moment, as well as most of the best-selling processors. As much as possible, the four test setups feature identical components, memory timings, drivers, etc. Aside from manually selecting memory frequencies and timings, every option in the BIOS was at its default setting.

Intel Core i3/i5/i7 LGA1156 Test Setup​

Intel Core i7 LGA1366 Test Setup​

AMD Phenom II AM3 Test Setup​

Intel Core 2 LGA775 Test Setup​

For all of the benchmarks, appropriate lengths are taken to ensure an equal comparison through methodical setup, installation, and testing. The following outlines our testing methodology:

A) Windows is installed using a full format.

B) Chipset drivers and accessory hardware drivers (audio, network, GPU) are installed followed by a defragment and a reboot.

C)To ensure consistent results, a few tweaks were applied to Windows Vista and the NVIDIA control panel:

• Sidebar – Disabled
• UAC – Disabled
• System Protection/Restore – Disabled
• Problem & Error Reporting – Disabled
• Remote Desktop/Assistance - Disabled
• Windows Security Center Alerts – Disabled
• Windows Defender – Disabled
• Screensaver – Disabled
• Power Plan - High Performance
• NVIDIA PhysX – Disabled
• V-Sync – Off

D) Programs and games are then installed & updated followed by another defragment.

E) Windows updates are then completed installing all available updates followed by a defragment.

F) Benchmarks are each ran three times after a clean reboot for every iteration of the benchmark unless otherwise stated, the results are then averaged. If they were any clearly anomalous results, the 3-loop run was repeated. If they remained, we will mention it in the indvidual benchmark write-up.

Here is a full list of the applications that we utilized in our benchmarking suite:

• 3DMark06 Professional v1.1.0
• 3DMark Vantage Professional Edition v1.0.1
• Cinebench R10 64-bit
• Crysis v1.21
• Far Cry 1.02
• HyperPi 0.99b
• Intel High Definition Experience and Performance Ratings Test 2009 (HDxPRT 2009) (Adobe Elements 7.0/QuickTime Player/iTunes 8.0.1/Sorenson Squeeze/PowerDVD 8/DiVX engine)
• Lame Front-End 1.0
• Lavalys Everest Ultimate v5.02.1834 Beta
• Left 4 Dead (Latest update)
• PCMark Vantage Advanced 64-Bit Edition (1.0.0.0)
• Photoshop CS4 Extended (64-bit)
• ScienceMark 2.0 Build 21MAR05
• SiSoft Sandra Professional 2009.9.15.124
• Street Fighter 4 Demo
• Supreme Commander v1.1.3280
• Valve Particle Simulation Benchmark
• WinRAR 3.8.0
• World in Conflict v1.0.0.0
• x264 HD Benchmark v1.0

That is about all you need to know methodology wise, so let's get to the good stuff!

 

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Synthetic Benchmarks: Everest CPU & Memory

Synthetic Benchmarks: Everest CPU & Memory

Lavalys Everest Ultimate

Everest Ultimate is the most useful tool for any and all benchmarkers or overclockers. With the ability to pick up most voltage, temperature, and fan sensors on almost every motherboard available, Everest provides the ability to customize the outputs in a number of forms on your desktop. We selected two of Everest's seven CPU benchmarks: CPU Queen and FPU Mandel. According to Lavalys, CPU Queen simple integer benchmark focuses on the branch prediction capabilities and the misprediction penalties of the CPU. It finds the solutions for the classic "Queens problem" on a 10 by 10 sized chessboard. At the same clock speed theoretically the processor with the shorter pipeline and smaller misprediction penalties will attain higher benchmark scores. The FPU Mandel benchmark measures the double precision (also known as 64-bit) floating-point performance through the computation of several frames of the popular "Mandelbrot" fractal. Both tests consume less than 1 MB system memory, and are HyperThreading, multi-processor (SMP) and multi-core (CMP) aware.

Lavalys Everest Ultimate

Everest Ultimate is the most useful tool for any and all benchmarkers or overclockers. With the ability to pick up most voltage, temperature, and fan sensors on almost every motherboard available, Everest provides the ability to customize the outputs in a number of forms on your desktop. In addition to this, the memory benchmarking utility provides a useful tool of measuring the changes to your memory sub-system.

Will ScienceMark 2.0 paint a different picture? Let's find out.


ScienceMark v2.0

Although last updated almost 3 years ago, and despite its rudimentary interface, ScienceMark v2.0 remains a favorite for accurately calculating bandwidth on even the newest chipsets.

These are just synthetic numbers though, real-life applications and games are what count. Let's check those out next.

 

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System Benchmarks: SuperPI 32M / wPRIME 1024M

System Benchmarks: SuperPI 32M / wPRIME 1024M

SuperPi Mod v1.5

When running the SuperPI 32MB benchmark, we are calculating Pi to 32 million digits and timing the process. Obviously more CPU power helps in this intense calculation, but the memory sub-system also plays an important role, as does the operating system. We are running one instance of SuperPi via the HyperPi 0.99b interface. This is therefore a single-thread workload.

wPRIME 2.03

wPrime is a leading multithreaded benchmark for x86 processors that tests your processor performance by calculating square roots with a recursive call of Newton's method for estimating functions, with f(x)=x2-k, where k is the number we're sqrting, until Sgn(f(x)/f'(x)) does not equal that of the previous iteration, starting with an estimation of k/2. It then uses an iterative calling of the estimation method a set amount of times to increase the accuracy of the results. It then confirms that n(k)2=k to ensure the calculation was correct. It repeats this for all numbers from 1 to the requested maximum. This is a highly multi-threaded workload.

 

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System Benchmarks: Cinebench R10 / Cinebench R11.5

System Benchmarks: Cinebench R10 / Cinebench R11.5

Cinebench R10

Cinebench R10 64-bit
Test1: Single CPU Image Render
Test2: Multi CPU Image Render
Comparison: Generated Score

Developed by MAXON, creators of Cinema 4D, Cinebench 10 is designed using the popular Cinema software and created to compare system performance in 3D Animation and Photo applications. There are two parts to the test; the first stresses only the primary CPU or Core, the second, makes use of up to 16 CPUs/Cores. Both are done rendering a realistic photo while utilizing various CPU-intensive features such as reflection, ambient occlusion, area lights and procedural shaders

Cinebench R11.5

Cinebench R11.5 64-bit
Test1: CPU Image Render
Comparison: Generated Score

The latest benchmark from MAXON, Cinebench R11.5 makes use of all your system's processing power to render a photorealistic 3D scene using various different algorithms to stress all available processor cores. The test scene contains approximately 2,000 objects containing more than 300,000 total polygons and uses sharp and blurred reflections, area lights and shadows, procedural shaders, antialiasing, and much more. This particular benchmarking can measure systems with up to 64 processor threads. The result is given in points (pts). The higher the number, the faster your processor.

 

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System Benchmarks: PCMark Vantage / Photoshop CS4

System Benchmarks: PCMark Vantage / Photoshop CS4

PCMark Vantage x64

PCMark Vantage Advanced 64-bit Edition (1.0.1.0)
PCMark Suite / Default Settings
Comparison: Generated Score

The main focus of our General Tasks category lies with the most recent installment of the PCMark series, Vantage. While still classified under the description of a Synthetic benchmark, PCMark Vantage uses many of Vista's (Note - Vantage is Vista-only) built-in programs and features along with its own tests, so it is "real-world" applicable in regards to CPU performance. The following is a general list of the tests in the PCMark suite, very much in line with tasks of an average user: Data encryption, Data compression, CPU image manipulation (compression/decompression/resize), Audio transcoding, Video transcoding, Text editing, Web page rendering, Windows Mail, Windows Contacts, and CPU game test.

Photoshop CS4

For the image editing portion of this review, we will use Photoshop CS4 in coordination with Driver Heaven’s Photoshop Benchmark V3, which is an excellent test of CPU power and memory bandwidth. This is a scripted benchmark that individually applies 15 different filters to a 109MB JPEG, and uses Photoshop’s built-in timing feature to provide a result at each test stage. Then it’s simply a matter of adding up the 15 results to reach the final figure.

 

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System Benchmarks: LFE / x264 HD / WinRAR

System Benchmarks: Lame Front End / x264 HD / WinRAR

Lame Front End

Lame Front End v1.0 is a single-threaded application, which means that it only utilizes a single processor core. This will obviously limit performance but it will allow us to gauge a processor's single-threaded performance as well as test any turbo feature that it might have. We will be encoding a WAV rip of Santana’s Supernatural album and converting it to MP3 using the highest fidelity VBR 0 quality preset.

x264 HD Benchmark

x264 HD Benchmark v1.0
Test: MPEG-2 HD 720P Video Clip Conversion to x264
DVD Video Length: 30 Seconds
Comparison: FPS of Second Pass

x264 is quickly becoming the new codec of choice for encoding a growing number of H.264/MPEG-4 AVC videos. Think of it as the new Divx of HD and you can understand why we felt it critical to include. Tech Arp's recent development of the x264 HD Benchmark takes a 30 second HD video clip and encodes it into the x264 codec with the intention of little to no quality loss. The test is measured using the average frames per second achieved during encoding, which scales with processor speed and efficiency. The benchmark also allows the use of multi-core processors so it gives a very accurate depiction of what to expect when using encoding application on a typical full length video.

WinRAR

WinRAR 3.8.0
Test: Compression of 1GB of Assorted Files
Comparison: Time to Finish

One of the most popular file compression/decompresion tools, we use WinRAR to compress a 1GB batch of files and archive them, timing the task until completion.

 

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Gaming Benchmarks: 3DMark06 / 3DMark Vantage

Gaming Benchmarks: 3DMark06 / 3DMark Vantage

Futuremark 3DMark06

3DMark06 v1.1.0
Graphic Settings: Default
Resolution: 1280X1024

Test: Specific CPU Score and Full Run 3Dmarks
Comparison: Generated Score

The Futuremark 3DMark series has been a part of the backbone in computer and hardware reviews since its conception. The trend continues today as 3DMark06 provides consumers with a solid synthetic benchmark geared for performance and comparison in the 3D gaming realm. This remains one of the most sought after statistics, as well as an excellent tool for accurate CPU comparison, and it will undoubtedly be used for years to come.

Futuremark 3DMark Vantage

3DMark Vantage v1.0.1
Graphic Settings: Performance Preset
Resolution: 1280X1024

Test: Specific CPU Score and Full Run 3Dmarks
Comparison: Generated Score

3DMark Vantage is the follow-up to the highly successful 3DMark06. It uses DirectX 10 exclusively so if you are running Windows XP, you can forget about this benchmark. Along with being a very capable graphics card testing application, it also has very heavily multi-threaded CPU tests, such Physics Simulation and Artificial Intelligence (AI), which makes it a good all-around gaming benchmark.