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Intel’s Core i5-655K & i7-875K Unlocked Processors

Date: May 28, 2010
Author(s): Rob Williams

Most of today’s desktop CPUs, including budget models, tend to be good for overclocking. But for those who are looking for the ultimate in tweaking ability, Intel’s mainstream models have left a bit to be desired. With the K series, though, it aims to remedy that situation by offering unlocked models at affordable prices.



Introduction

For years, AMD has been offering “Black Edition” processors that cater both to the consumer who wants the best AMD has to offer, and overclockers who want as much flexibility as possible. The reason is unlocked ratios and multipliers, something that on the Intel side required expensive “Extreme Edition” processors.

Given that Intel has been on top of the processor game for years now, it’s difficult to say that the company has finally caught up in this regard, but it has. There’s no fancy naming scheme here, though… simply a “K” at the end of the model number is all you need to look for, or alternatively, the word “Unlocked” on the box.

K processor models have a near identical non-K model. The differences are that the K models are unlocked, meaning that they can be overclocked without affecting other PC components, such as your RAM. So, if you’re looking for a massive CPU overclock, you don’t have to worry too much about purchasing a super-fast kit of memory to support it – unless you’re looking for the best of both worlds.

As you would expect, K models carry a bit of a cost premium, but as it stands, the only other way to have an unlocked Intel CPU is to purchase an Extreme Edition, which is obviously even more costly. K models essentially allow any enthusiast overclocker to have some unlocked fun, without splurging on an Extreme Edition.

Intel Core i7 K Series Box Art Intel Core i7 K Series Box Art

For this launch, Intel has released two different K models. The highest-end is the Core i7-875K, which is specced identically to the Core i7-870, and it happens to be a blazing fast processor. It’s of course a quad-core with eight threads, and features 8MB of L3 Cache. As it’s based on Lynnfield, it doesn’t feature a 32nm process, or the AES instruction set. This model is clocked at 2.93GHz and can hit 3.60GHz on some cores thanks to Turbo, depending on the workload.

Second, there is the Core i5-655K, which is based on the Core i5-650. This Clarkdale model does feature a 32nm process and the AES instruction set, and is clocked at 3.20GHz, with Turbo boosting that to 3.42GHz. Also as a Clarkdale model, this CPU features an integrated GPU, although something tells me that enthusiast overclockers will not likely be making too much use of it.

Intel CPU
Cores
Threads
Clock
Turbo
Cache
GPU
TDP
1Ku Price
Core i7-980X (4)
6
12
3.33GHz
3.60GHz
12MB
N/A
130W
$999
Core i7-975 (1)
4
8
3.33GHz
3.60GHz
8MB
N/A
130W
$999
Core i7-960 (1)
4
8
3.20GHz
3.46GHz
8MB
N/A
130W
$562
Core i7-950 (1)
4
8
3.06GHz
3.33GHz
8MB
N/A
130W
$562
Core i7-870 (2)
4
8
2.93GHz
3.60GHz
8MB
N/A
95W
$562
Core i7-875K (2)
4
8
2.93GHz
3.60GHz
8MB
N/A
95W
$342
Core i7-860S (2)
4
8
2.53GHz
3.46GHz
8MB
N/A
82W
$337
Core i7-930 (1)
4
8
2.80GHz
3.06GHz
8MB
N/A
130W
$294
Core i7-860 (2)
4
8
2.80GHz
3.46GHz
8MB
N/A
95W
$284
Core i7-920 (1)
4
8
2.66GHz
2.93GHz
8MB
N/A
130W
$284
Core i5-670 (3)
2
4
3.46GHz
3.73GHz
4MB
733MHz
73W
$284
Core i5-750S (2)
4
4
2.40GHz
3.20GHz
8MB
N/A
82W
$259
Core i5-655K (3)
2
4
3.20GHz
3.46GHz
4MB
733MHz
73W
$216
Core i5-750 (2)
4
4
2.66GHz
3.20GHz
8MB
N/A
95W
$196
Core i5-661 (3)
2
4
3.33GHz
3.60GHz
4MB
900MHz
87W
$196
Core i5-660 (3)
2
4
3.33GHz
3.60GHz
4MB
733MHz
73W
$196
Core i5-650 (3)
2
4
3.20GHz
3.46GHz
4MB
733MHz
73W
$176
Core i3-540 (3)
2
4
3.06GHz
N/A
4MB
733MHz
73W
$133
Core i3-530 (3)
2
4
2.93GHz
N/A
4MB
733MHz
73W
$113
Pentium G6950 (3)
2
2
2.80GHz
N/A
3MB
533MHz
73W
$87
Microarchitecture: (1) Bloomfield, (2) Lynnfield, (3) Clarkdale, (4) Gulftown

As you can see from the images at the top of the page, Intel has also altered the box art for the K processors, but not by much. Unlike AMD, which sells its unlocked models in a black box (rather than purple or green), Intel has opted to add the word “Unlocked” to its boxes, still making them easy to spot at retail.

I mentioned earlier that there would be some slight premiums on K models, but there’s an exception with these launch models. The i5-655K is priced $40 higher than the i5-650, while the i7-875K is priced well below the i7-870 (which would lead us to believe that Intel is phasing it out). Compared to the Core i7-860, the i7-875K carries a $58 premium, but is clocked faster (2.93GHz vs. 2.80GHz).

Alongside this launch, Intel is also pushing its launch top-end P55 model, the DP55KG, which it feels is suitable for high-end overclocking. Unfortunately, due to this launch occurring so close to Computex, and planning for that dominated so much of my time the past couple of weeks, I was unable to use Intel’s board for the task, and opted to stick with the board I was already used to overclocking with.

Once back from the show, I’ll give the company’s board with latest BIOS a proper test, and see just how far it can be pushed. I’ve had poor luck overclocking with Intel’s boards in the past, but during a meeting during this year’s CES, the company reassured us that it was putting much more of a focus on overclocking going-forward, so I look forward to spending some honest time with the board once I return.

Overall, there’s not much else to say about these processors, as we’ve already written in-depth articles on each respective architecture. Who are the K models for? I’m of the opinion that they’re either for those who really don’t want to splurge on a higher-end kit of RAM, or hardcore overclockers – both of whom would want to go well beyond the 4.0GHz mark.

With that said, let’s tackle our test system and methodology, than move right into our performance and overclocking results.

Test System & Methodology

At Techgage, we strive to make sure our results are as accurate as possible. Our testing is rigorous and time-consuming, but we feel the effort is worth it. In an attempt to leave no question unanswered, this page contains not only our testbed specifications, but also a fully-detailed look at how we conduct our testing.

If there is a bit of information that we’ve omitted, or you wish to offer thoughts or suggest changes, please feel free to shoot us an e-mail or post in our forums.

Test System

The table below lists the hardware for our two current machines, which remains unchanged throughout all testing, with the exception of the processor. Each CPU used for the sake of comparison is also listed here, along with the BIOS version of the motherboard used. In addition, each one of the URLs in this table can be clicked to view the respective review of that product, or if a review doesn’t exist, you will be led to the product on the manufacturer’s website.

Please note that for benchmarking the Core i7-980X, we deviated from the Rampage II Extreme that we tested all other Bloomfield’s with in favor of taking Gigabyte’s X58A-UD5 for a spin. This motherboard change won’t effect the performance, but it will change the power consumption just a wee bit. As mentioned before, we’re in the process of upgrading our entire CPU test suite, and the X58A-UD5 will become the base of our new LGA1366 test platform.

Component
AMD AM2+/AM3 Test System
Processors

AMD Phenom II X4 965 Black Edition – Quad-Core, 3.40GHz, 1.325v
AMD Phenom II X4 955 Black Edition – Quad-Core, 3.20GHz, 1.325v
AMD Phenom II X3 720 Black Edition – Tri-Core, 2.80GHz, 1.325v
AMD Phenom II X2 555 Black Edition – Dual-Core, 3.20GHz, 1.325v

AMD Athlon II X4 635 – Quad-Core, 2.90GHz, 1.325v
AMD Athlon II X4 620 – Quad-Core, 2.60GHz, 1.375v
AMD Athlon II X3 435 – Tri-Core, 2.90GHz, 1.325v
AMD Athlon II X2 240e – Dual-Core, 2.80GHz, 1.325v
Motherboard
Gigabyte MA790GP-DS4H – 790GX-based, F3 BIOS (01/13/09)
Memory

Corsair XMS3 DHX 2x2GB – DDR3-1333 7-7-7-20-2T, 1.65v
Graphics
Audio
On-Board Audio
Storage

Intel X-25M 80GB SSD
Seagate Barracuda 500GB 7200.11
Power Supply
Corsair HX1000W
Chassis
SilverStone TJ10 Full-Tower
Display
Gateway XHD3000 30″
Cooling
Thermaltake V1
Et cetera
Windows Vista Ultimate 64-bit

Component
Intel LGA1156 Test System
ProcessorsIntel Core i7-870K – Quad-Core, 2.93GHz, ~1.25v
Intel Core i7-870 – Quad-Core, 2.93GHz, ~1.25v
Intel Core i5-750 – Quad-Core, 2.66GHz, ~1.25v
Intel Core i5-665K – Dual-Core, 3.20GHz, ~1.25v
Intel Core i5-661 – Dual-Core, 3.33GHz, ~1.10v
Intel Core i3-530 – Dual-Core, 2.93GHz, ~1.00v
Motherboard
Lynnfield: Gigabyte P55-UD5 – P55-based, F3 BIOS (08/01/09)
Westmere: ASUS P7H55D-M EVO – H55-based, 0503 BIOS (12/02/09)
Memory

Corsair XMS3 DHX 2x2GB – DDR3-1333 7-7-7-20-2T, 1.65v
Graphics
ATI Radeon HD 4870 512MB (Catalyst 8.11)
Audio
On-Board Audio
Storage

Intel X-25M 80GB SSD
Seagate Barracuda 500GB 7200.11
Power Supply
Corsair HX1000W
Chassis
SilverStone TJ10 Full-Tower
Display
Gateway XHD3000 30″
Cooling
Thermalright MUX-120
Et cetera
Windows Vista Ultimate 64-bit

Component
Intel LGA1366 Test System
Processors

Intel Core i7-980X Extreme Edition
Six-Core, 3.33GHz, 1.30v
Intel Core i7-975 Extreme Edition – Quad-Core, 3.33GHz, 1.30v
Intel Core i7-965 Extreme Edition – Quad-Core, 3.33GHz, 1.30v
Intel Core i7-920 Quad-Core, 2.66GHz, 1.30v
Motherboard
ASUS Rampage II Extreme – X58-based, 0705 BIOS (11/21/08)
Gigabyte X58A-UD5 – X58-based, F4 BIOS (02/12/10)
(Gigabyte’s board used only for Core i7-980X)
Memory

OCZ Gold 3x2GB – DDR3-1066 7-7-7-20-1T, 1.56v (920/940)
OCZ Gold 3x2GB – DDR3-1600 7-7-7-20-1T, 1.56v (965/975/980X)
Graphics
Audio
On-Board Audio
Storage
Intel X-25M 80GB SSD

Seagate Barracuda 500GB 7200.11
Power Supply
SilverStone DA1200
Chassis
SilverStone TJ10 Full-Tower
Display
Gateway XHD3000 30″
Cooling
Thermalright TRUE Black 120
Et cetera
Windows Vista Ultimate 64-bit

Component
Intel LGA775
Processors

Intel Core 2 Quad Q9650 – Quad-Core, 3.00GHz, 1.30v (Sim)
Intel Core 2 Quad Q9550 – Quad-Core, 2.83GHz, 1.30v (Sim)
Intel Core 2 Quad Q9400 – Quad-Core, 2.66GHz, 1.30v
Intel Core 2 Quad Q8200 – Quad-Core, 2.33GHz, 1.30v
Intel Core 2 Duo E8600 – Dual-Core, 3.33GHz, 1.30v
Intel Core 2 Duo E8500 – Dual-Core, 3.16GHz, 1.30v (Sim)
Intel Core 2 Duo E8400 – Dual-Core, 3.00GHz, 1.30v
Intel Pentium Dual-Core E5200 – Dual-Core 2.50GHz, 1.30v
Motherboard
ASUS Rampage Extreme – X48-based, 0501 BIOS (08/28/08)
Memory

Corsair XMS3 DHX 2x2GB – DDR3-1333 7-7-7-15-1T, 1.91v (1333FSB)
Corsair XMS3 DHX 2x2GB – DDR3-1066 6-6-6-15-1T, 1.91v (1066FSB)
Corsair XMS3 DHX 2x2GB – DDR3-800 6-6-6-15-1T, 1.91v (800FSB)

Graphics
Audio
On-Board Audio
Storage
Intel X-25M 80GB SSD

Seagate Barracuda 500GB 7200.11
Power Supply
Corsair HX1000W
Chassis
SilverStone TJ10 Full-Tower
Display
Gateway XHD3000 30″
Cooling
Thermalright TRUE Black 120
Et cetera
Windows Vista Ultimate 64-bit

(Sim) represents models that were tested using a faster, but under-clocked processor. For example, for the Q9550, we used the QX9770, since the specs are identical all-around, except for the clock speeds. Those were adjusted appropriately, effectively giving us a Q9550 to test with.

When preparing our testbeds for any type of performance testing, we follow these guidelines:

To aide with the goal of keeping accurate and repeatable results, we alter certain services in Windows Vista from starting up at boot. This is due to the fact that these services have the tendency to start up in the background without notice, potentially causing slightly inaccurate results. Disabling “Windows Search” turns off the OS’ indexing which can at times utilize the hard drive and memory more than we’d like.

Application Benchmarks

To help test out the real performance benefits of a given processor, we run a large collection of both real-world and synthetic benchmarks, including 3ds Max, Adobe Lightroom, TMPGEnc Xpress, Sandra 2009 and many more.

Our ultimate goal is always to find out which processor excels in a given scenario and why. Running all of the applications in our carefully-chosen suite can help better give us answers to those questions. Aside from application data, we also run two common games to see how performance scales there, including Call of Duty 4 and Half-Life 2: Episode Two.

Game Benchmarks

In an attempt to offer “real-world” results, we do not utilize timedemos in any of our reviews. Each game in our test suite is benchmarked manually, with the minimum and average frames-per-second (FPS) captured with the help of FRAPS 2.9.5.

To deliver the best overall results, each title we use is exhaustively explored in order to find the best possible level in terms of intensiveness and replayability. Once a level is chosen, we play through repeatedly to find the best possible route and then in our official benchmarking, we stick to that route as close as possible. Since we are not robots and the game can throw in minor twists with each run, no run can be identical to the pixel.

Each game and setting combination is tested twice, and if there is a discrepancy between the initial results, the testing is repeated until we see results we are confident with.

The two games we currently use for our motherboard reviews are listed below, with direct screenshots of the game’s setting screens and explanations of why we chose what we did.

Call of Duty: World at War

1680×1050
2560×1600




Crysis Warhead

1680×1050
2560×1600




Half-Life 2: Episode Two

1680×1050
2560×1600

Workstation: Autodesk 3ds Max, Cinebench, POV-Ray

Autodesk’s 3ds Max is without question an industry standard when it comes to 3D modeling and animation, with DreamWorks, BioWare and Blizzard Entertainment being a few of its notable users. It’s a multi-threaded application that’s designed to be right at home on multi-core and multi-processor workstations or render farms, so it easily tasks even the biggest system we can currently throw at it.

For our testing, we use two project files that are designed to last long enough to find any weakness in our setup and also allows us to find a result that’s easily comparable between both motherboards and processors. The first project is a dog model included on recent 3ds Max DVD’s, which we infused with some Techgage flavor.

Our second project is a Bathroom scene that makes heavy use of ray tracing. Like the dog model, this one is also included with the application’s sample files DVD. The dog is rendered at an 1100×825 resolution, while the Bathroom is rendered as 1080p (1920×1080).

Cinebench R10

Like 3DS Max, Cinema 4D is another popular cross-platform 3D graphics application that’s used by new users and experts alike. Its creators, Maxon, are well aware that their users are interested in huge computers to speed up rendering times, which is one reason why they released Cinebench to the public.

Cinebench R10 is based on the Cinema 4D engine and the test consists of rendering a high-resolution model of a motorcycle and gives a score at the end. Like most other 3D applications on the market, Cinebench will take advantage of as many cores as you can throw at it.

POV-Ray 3.7

Similar to Cinebench, the “Persistence of Vision Ray Tracer” is as you’d expect, a ray tracing application that also happens to be cross-platform. It allows you to take your environment and models and apply a ray tracing algorithm, based on a script you either write yourself or borrow from others. It’s a free application and has become a standard in the ray tracing community and some of the results that can be seen are completely mind-blowing.

The official version of POV-Ray is 3.6, but the 3.7 beta unlocks the ability to take full advantage of a multi-core processor, which is why we use it in our testing. Applying ray tracing algorithms can be extremely system intensive, so this is one area where multi-core processors will be of true benefit.

For our test, we run the built-in benchmark, which delivers a simple score (Pixels-Per-Second) the the end. The higher, the better. If one score is twice another, it does literally mean it rendered twice as fast.

As we explore all of our results throughout the article, there will be two common trends. The first is that the Core i7-875K will perform almost identically to the Core i7-870, as it’s essentially the same CPU – save for the unlocked ratios. For the Core i5-655K, we should see it compete nicely to the Core i5-661.

Although the i5-661 is faster, the i5-655K surpassed its performance here, which is nonsensical. In all likeliness, we have the motherboard’s BIOS to thank, as multiple new versions have been released since we tested the i5-661.

Multi-Media: Adobe Lightroom, TMPGEnc Xpress

Photo manipulation benchmarks are more relevant than ever, given the proliferation of high-end digital photography hardware. For this benchmark, we test the system’s handling of RAW photo data using Adobe Lightroom, an excellent RAW photo editor and organizer that’s easy to use and looks fantastic.

For our testing, we take 100 RAW files (in Nikon’s .NEF file format) which have a 10-megapixel resolution, and export them as JPEG files in 1000×669 resolution, similar to most of the photos we use here on the website. Such a result could also be easily distributed online or saved as a low-resolution backup. This test involves not only scaling of the image itself, but encoding in a different image format. The test is timed indirectly using a stopwatch, and times are accurate to within +/- 0.25 seconds.

TMPGEnc Xpress 4.5

When it comes to video transcoding, one of the best offerings on the market is TMPGEnc Xpress. Although a bit pricey, the software offers an incredible amount of flexibility and customization, not to mention superb format support. From the get go, you can output to DivX, DVD, Video-CD, Super Video-CD, HDV, QuickTime, MPEG, and more. It even goes as far as to include support for Blu-ray video!

There are a few reasons why we choose to use TMPGEnc for our tests. The first relates to the reasons laid out above. The sheer ease of use and flexibility is appreciated. Beyond that, the application does us a huge favor by tracking the encoding time, so that we can actually look away while an encode is taking place and not be afraid that we’ll miss the final encoding time. Believe it or not, not all transcoding applications work like this.

For our test, we take a 0.99GB high-quality DivX H.264 AVI video of Half-Life 2: Episode Two gameplay with stereo audio and transcode it to the same resolution of 720p (1280×720), but lower the bit rate in order to attain a modest file size. This test also utilizes the SSE instruction sets, either SSE2 or SSE4, depending on what the chip supports.

The Core i5-655K continues its trend of dominating the Core i5-661 here, furthering our belief that BIOS updates can perform miracles from time to time. It would be unfair to retain incomparable results for too much longer, but thankfully we’ll be soon to complete our CPU testing suite revision, so that will give us completely fresh results from every model.

Multi-Media: ProShow Gold, Sandra Multi-Media

While TMPGEnc XPress’ purpose is to convert video formats, ProShow from Photodex helps turn your collection of photos into a fantastic-looking slide show. I can’t call myself a slide show buff, but this tool is unquestionably definitive. It offers many editing abilities and the ability to export in a variety of formats, including a standard video file, DVD video and even HD video.

Like TMPGEnc and many other video encoders, ProShow can take full advantage of a multi-core processor. It doesn’t support SSE4 however, but hopefully will in the future as it would improve encoding times considerably. Still, when a slide show application handles a multi-core processor effectively, it has to make you wonder why there is such a delay in seeing a wider-range of such applications on the marketplace.

Once again, the Core i7-875K performs on par with the Core i7-870, and the Core i5-655K continues to perform well.

Sandra 2009 Multi-Media

This test here stresses the CPU’s ability to handle multi-media instructions and data, using both MMX and SSE2/3/4 as the instruction sets of choice. The results are divided by integer, floating point and double precision, three specific numbering formats used commonly in multi-media work.

Leave it to a synthetic benchmark to show us just what we wanted to see… a 50% increase. We call these synthetic benchmarks for a reason, because in the real-world, as we’ve seen, it’s very hard to exploit all six cores at once, or even come close to an actual 50% increase.

Mathematics: Sandra Arithmetic, Crypto, Microsoft Excel

With each new processor launch, one thing that’s bound to prove faster are mathematical equations, which when all said and done, plays a massive role in a lot of our computing today. The faster an equation can be completed, the faster a math-heavy process can finish.

Sandra includes applications designed to specifically test the mathematical performance of processors, with the main one being the arithmetic test.

As expected, like Sandra’s multimedia test, the arithmetic test does well to use every bit of processor you give it, so we once again see a near-perfect 50% performance gain.

Sandra 2009 Cryptography

Crypto is a major part of computing, whether you know it or not, and certain processes can prove slower than others, depending on their algorithms. User passwords on your home PC are encrypted, as are user passwords on web servers (like in our forums). Past that, crypto is used in other areas as well, such as with creating of unbreakable locks on files or assigning a hash to a particular file (like MD5).

In Sandra’s Cryptography test, the results are outputted as MB/s, higher being better. Although this is somewhat of an odd metric to go by, generally speaking, the higher the number, the faster the CPU tears through the respective algorithm, which comes down to how fast a password is either encrypted, decrypted, signed, et cetera.

Those who own Clarkdale processors are certainly spoiled where AES encryption is concerned. The Core i7-875K is still stuck behind with lower scores thanks to its lack of the AES encryption set, while the Core i7-655K soars nearly to the top of the charts.

Microsoft Excel 2007

Most, if not all, businesses in existence have to crack open a spreadsheet at some point. Though simple in concept, spreadsheets are an ideal way to either track information or compute large calculations all in real-time. This is important when you run a business that deals with a large amount of expenses.

Although the importance of how fast a calculation takes in an Excel file is, we include results here since they heavily test the mathematical capabilities of each processor. Because Excel 2007 is completely multi-threaded (it can even take advantage of an 8-Core Skulltrail), it makes for a great benchmark to show the scaling between all of our CPUs.

I’ll let Intel explain the two files we use:

Monte CarloThis workload calculates the European Put and Call option valuation for Black-Scholes option pricing using Monte Carlo simulation. It simulates the calculations performed when a spreadsheet with input parameters is updated and must recalculate the option valuation. In this scenario we execute approximately 300,000 iterations of Monte Carlo simulation. In addition, the workload uses Excel lookup functions to compare the put price from the model with the historical market price for 50,000 rows to understand the convergence. The input file is a 70.1 MB spreadsheet.

CalculationsThis workload executes approximately 28,000 sets of calculations using the most common calculations and functions found in Excel*. These include common arithmetic operations like addition, subtraction, division, rounding and square root. It also includes common statistical analysis functions such as Max, Min, Median and Average. The calculations are performed after a spreadsheet with a large dataset is updated with new values and must re-calculate many data points. The input file is a 6.2 MB spreadsheet.

Excel might seem innocent enough, but it’s easily one of the most multi-threaded applications on the market. It’s going to be awful difficult for a regular user to ever require more than one core, but for those with extremely robust spreadsheets replete with calculations, multi-core processors can help.

System: Sandra Memory, Multi-Core Efficiency

Generally speaking, the faster the processor, the higher the system-wide bandwidth and the lower the latency. As is always the case, faster is better when it comes to processors, as we’ll see below. But with Core i7, the game changes up a bit.

Whereas previous memory controllers utilized a dual-channel operation, Intel threw that out the window to introduce triple-channel, which we talked a lot about at August’s IDF. Further, since Intel integrates the IMC onto the die of the new CPUs, benefits are going to be seen all-around.

Before jumping into the results, we already had an idea of what to expect, and just as we did, the results seen are nothing short of staggering.

As Clarkdale’s microarchitecture changed where the IMC is located, the speed in bandwidth and latencies has been decreased ever-so-slightly with the Core i5-655K. The Core i7-875K performs very well, near the top of the charts.

Thanks again to BIOS improvements, the Core i5-655K sees nice gains over the Core i5-661, which again was benchmarked long ago with an older BIOS. The Core i7-875K on the other hand performed near-identically to the Core i7-870, which is what we expected given their stark similarities.

Sandra 2009 Multi-Core Efficiency

How fast can one core swap data with another? It might not seem that important, but it definitely is if you are dealing with a true multi-threaded application. The faster data can be swapped around, the faster it’s going to be finished, so overall, inter-core speeds are important in every regard.

Even without looking at the data, we know that Core i7 is going to excel here, for a few different reasons. The main is the fact that this is Intel’s first native Quad-Core. Rather than have two Dual-Core dies placed beside each other, i7 was built to place four cores together, so that in itself improves things. Past that, the ultra-fast QPI bus likely also has something to do with speed increases.

As far as multi-core handshaking goes, Intel reigns supreme. Even AMD’s latest Phenom II’s come nowhere close to Intel’s last-generation Core 2’s.

Gaming: Call of Duty: World at War, Half-Life 2: Episode Two

While some popular game franchises are struggling to keep themselves healthy, Call of Duty doesn’t have much to worry about. This is Treyarch’s third go at a game in the series, and a first for one that’s featured on the PC. All worries leading up to this title were all for naught, though, as Treyarch delivered on all promises.

To help keep things fresh, CoD: World at War focuses on battles not exhaustively explored in previous WWII-inspired games. These include battles which take place in the Pacific region, Russia and Berlin, and variety is definitely something this game pulls off well, so it’s unlikely you’ll be off your toes until the end of the game.

For our testing, we use a level called “Relentless”, as it’s easily one of the most intensive levels in the game. It features tanks, a large forest environment and even a few explosions. This level depicts the Battle of Peleliu, where American soldiers advance to capture an airstrip from the Japanese. It’s a level that’s both exciting to play and one that can bring even high-end systems to their knees.

Luckily for hardcore CoD players, the game’s performance doesn’t change with a faster CPU, which is rather impressive. Here, the game ran just as well on our lowly E5200 as it did on our i7-980X.

Half-Life 2: Episode Two

The original Half-Life 2 might have first seen the light of day close to four years ago, but it’s still arguably one of the greatest-looking games ever seen on the PC. Follow-up versions, including Episode One and Episode Two, do well to put the Source Engine upgrades to full use. While playing, it’s hard to believe that the game is based on a four+ year old engine, but it still looks great and runs well on almost any GPU purchased over the past few years.

Like Call of Duty 4, Half-Life 2: Episode Two runs well on modest hardware, but a recent mid-range graphics card is recommended if you wish to play at higher than 1680×1050 or would like to top out the available options, including anti-aliasing and very high texture settings.

This game benefits from both the CPU and GPU, and the skies the limit. In order to fully top out the available settings and run the highest resolution possible, you need a very fast GPU or GPUs along with a fast processor. Though the in-game options go much higher, we run our tests with 4xAA and 8xAF to allow the game to remain playable on the smaller mid-range cards.

Unlike CoD, HL2: Episode Two does love extra CPU power, and that’s evidenced above, but only at the highly-sporadic 1680×1050 resolution. That resolution has proven to be a chore, because the average FPS can fluctuate a great deal. What’s important to note here is that at our top setting of 2560×1600, the differences are almost zero.

Gaming: Crysis Warhead, 3DMark Vantage

As PC enthusiasts, we tend to be drawn to games that offer spectacular graphics… titles that help reaffirm your belief that shelling out lots of cash for that high-end monitor and PC was well worth it. But it’s rare when a game comes along that is so visually-demanding, it’s unable to run fully maxed out on even the highest-end systems on the market. In the case of the original Crysis, it’s easy to see that’s what Crytek was going for.

Funny enough, even though Crysis was released close to a year ago, the game today still has difficulty running at 2560×1600 with full detail settings – and that’s even with overlooking the use of anti-aliasing! Luckily, Warhead is better optimized and will run smoother on almost any GPU, despite looking just as gorgeous as its predecessor, as you can see in the screenshot below.

The game includes four basic profiles to help you adjust the settings based on how good your system is. These include Entry, Mainstream, Gamer and Enthusiast – the latter of which is for the biggest of systems out there, unless you have a sweet graphics card and are only running 1680×1050. We run our tests at the Gamer setting as it’s very demanding on any current GPU and is a proper baseline of the level of detail that hardcore gamers would demand from the game.

Our previous games didn’t show real differences between CPUs, and Crysis Warhead is no different. You can be rest-assured that no matter your PC, this game is going to run like molasses!

Futuremark 3DMark Vantage

Although we generally shun automated gaming benchmarks, we do like to run at least one to see how our GPUs scale when used in a ‘timedemo’-type scenario. Futuremark’s 3DMark Vantage is without question the best such test on the market, and it’s a joy to use, and watch. The folks at Futuremark are experts in what they do, and they really know how to push that hardware of yours to its limit.

The company first started out as MadOnion and released a GPU-benchmarking tool called XLR8R, which was soon replaced with 3DMark 99. Since that time, we’ve seen seven different versions of the software, including two major updates (3DMark 99 Max, 3DMark 2001 SE). With each new release, the graphics get better, the capabilities get better and the sudden hit of ambition to get down and dirty with overclocking comes at you fast.

Similar to a real game, 3DMark Vantage offers many configuration options, although many (including us) prefer to stick to the profiles which include Performance, High and Extreme. Depending on which one you choose, the graphic options are tweaked accordingly, as well as the resolution. As you’d expect, the better the profile, the more intensive the test.

Performance is the stock mode that most use when benchmarking, but it only uses a resolution of 1280×1024, which isn’t representative of today’s gamers. Extreme is more appropriate, as it runs at 1920×1200 and does well to push any single or multi-GPU configuration currently on the market – and will do so for some time to come.

The results here are rather predictable, given 3DMark’s rather clean scaling ability.

Overclocking Intel’s Core i5-655K & Core i7-875K

Before discussing results, let’s take a minute to briefly discuss what I consider to be a worthwhile overclock. As I’ve mentioned in past content, I’m not as interested in finding the highest overclock possible as much as I am interested in finding the highest stable overclock. To me, if an overclock crashes the computer after a few minutes of running a stress-test, it has little value except for competition.

How we declare an overclock stable is simple… we stress it as hard as possible for a certain period of time, both with CPU-related tests and also GPU-related, to conclude on what we’ll be confident is 100% stability throughout all possible computing scenarios.

For the sake of CPU stress-testing, we use LinX. Compared to other popular CPU stress-testers, LinX’s tests are far more grueling, and proof of that is seen by the fact that it manages to heat the CPU up to 20°C hotter than competing applications, like SP2004. Also, LinX is just as effective on AMD processors. Generally, if the CPU survives the first half-hour of this stress, there’s a good chance that it’s mostly stable, but I strive for a 12 hour stress as long as time permits.

If the CPU stress passes without error, then GPU stress-testing begins, in order to assure a system-wide stable overclock. To test for this, 3DMark Vantage’s Extreme test is used, with the increased resolution of 2560×1600, looped nine times. If this passes, some time is dedicated to real-world game testing, to make sure that gaming is just as stable as it would be if the CPU were at stock. If both these CPU and GPU tests pass without issue, we can confidently declare a stable overclock.

Overclocking Intel’s Core i5-655K & Core i7-875K

To preface our overclocking report, I’d like to mention that due to the overall tight timing of this embargo, I wasn’t able to devote as much time to overclocking these two processors as I would have liked, due to other performance testing for other content needing to be done at around the same time.

For stable overclocks, I like to stress test for up to eight hours if possible, but here, I just went for 40 minutes for each run of LinX for the sake of time. If I hit that, then I decided to benchmark with it. I can’t consider these clocks truly stable, however, due to the fact that I couldn’t stress them for far longer.

To kick things off, the i5-655K overclocked like a dream, as was to be expected given that it’s a dual-core model, and that our previous Clarkdale overclocking adventures delivered similar results. The difference here, though, is that our RAM speeds didn’t leave DDR3-1333.

To reach 4.56GHz, I had to use a rather high voltage of about 1.475V, and 1.500V for the QPI bus. Even though the BCLK wasn’t drastically changed, the extra voltage was needed for any sort of stability – even when we kept it at 133MHz.

Intel Core i5-655K Overclock

Intel Core i5-655K 3.20GHz (Overclock: 4.56GHz)
Benchmark
Stock
Overclock
Increase
Autodesk 3ds Max 2009
Dog Render
Bathroom Render
307 s
731 s
194 s
490 s
36.81%
32.97%
Cinebench R10
Single-Thread
Multi-Thread
4866
11020
6267

13921
28.79%
26.32%
POV-Ray 3.7
Single-Thread
Multi-Thread
881.61
2257.24

1169.88
3015.26

31.70%
33.58%

Adobe Lightroom 2.0
Convert 100 RAW to JPEG
129.46 s

122.10 s

5.69%

TMPGEnc Xpress
HD Video Encode
Mobile Video Encode

265 s
110 s


213 s
89 s


19.62%
21.24%

ProShow Gold
HD Video Encode
DVD Video Encode

451 s
113 s


349 s
88
s


22.62%

22.12%

Sandra Arithmetic
Dhrystone SSE4.2
Whetstone SSE3

50280
MIPS
36390 MFLOPS


56590 MIPS
40964 MFLOPS


12.55%
12.57%

Sandra Multi-Media
Int x16
Float x8
Double x4

91.41 MPixel/s
68.92 MPixel/s
37.5 MPixel/s


121.94 MPixel/s
91.94 MPixel/s
50.35 MPixel/s


33.41%
33.40%
34.27%

Sandra Cryptography
AES256
SHA256

3623
446


2960
594


-18.3%
33.18%

Microsoft Excel
Monte Carlo
Big Number Crunch

27.268 s
8.018 s


21.403 s
6.381 s


21.51%
20.42%

3DMark Vantage
Performance CPU

10053


12739


26.72%

As expected, the performance increases with our overclock scaled rather well, with the exception of some benchmarks, such as Lightroom. Oddly, the AES256 saw the same kind of decrease from overclocking that we saw with our Core i7-980X Extreme Edition review. I’m unable to explain this, as every-single other benchmark saw an improvement, but it was consistent.

Although it’s more difficult to overclock a quad-core compared to a dual-core, I had an even more difficult time overclocking the i7-875K than I expected. To hit 4.12GHz was a challenge. I didn’t have to use voltages quite as high as I did for the i5-655K, but that’s because it didn’t seem to help at all. But again, more time might need to be spent in order to get a better overall clock.

Intel Core i5-655K Overclock

Intel Core i5-875K 2.93GHz (Overclock: 4.12GHz)
Benchmark
Stock
Overclock
Increase
Autodesk 3ds Max 2009
Dog Render
Bathroom Render
189 s
404 s
126 s
276 s
33.33%
31.68%
Cinebench R10
Single-Thread
Multi-Thread
4431
18371
5568
22961
25.66%
24.99%
POV-Ray 3.7
Single-Thread
Multi-Thread
867.44
3937.3

1155.08
5041.33

33.16%
28.03%

Adobe Lightroom 2.0
Convert 100 RAW to JPEG
96.17 s

89.89 s

6.53%

TMPGEnc Xpress
HD Video Encode
Mobile Video Encode

197 s
105 s


167 s
88 s


15.23%
16.19%

ProShow Gold
HD Video Encode
DVD Video Encode

237 s
63 s


196 s
52
s

17.3%
17.47%

Sandra Arithmetic
Dhrystone SSE4.2
Whetstone SSE3

77718 MIPS
61068 MFLOPS


89640 MIPS
70631 MFLOPS


15.34%
15.66%

Sandra Multi-Media
Int x16
Float x8
Double x4

163.01 MPixel/s
125.22 MPixel/s
69.11 MPixel/s


214.43 MPixel/s
164.05 MPixel/s
90.69 MPixel/s


31.54%
31.01%
31.23%

Sandra Cryptography
AES256
SHA256

581
532


789
723


35.80%
35.90%

Microsoft Excel
Monte Carlo
Big Number Crunch

13.571 s
4.088 s


11.351 s
3.553 s


16.36%
13.09%

3DMark Vantage
Performance CPU

19017


23600


24.10%

Once again, the scaling is quite good. We don’t have the oddball AES decrease here, as we saw with the i5-655K, so it seems likely that the AES instruction set has something to do with that oddity. It does seem strange that overclocking can worsen the performance there, and it’s something I plan to investigate in the near-future.

Overall, these processors deliver just the kind of overclocking I was expecting. As far as I can tell, and based on all of the information Intel has given us, K processors are not cherry-picked. That means that aside from their unlocked likeness, their top-end overclocks shouldn’t vary too much from current Clarkdale and Lynnfield models.

Power Consumption

It goes without saying that power efficiency is at the forefront of many consumers’ minds today, and for good reason. Whether you are trying to save money or the environment – or both – it’s good to know just how much effort certain vendors are putting into their products to help them excel in this area. Both AMD and Intel have worked hard to develop efficient chips, and that’s evident with each new launch. The CPUs are getting faster, and use less power, and hopefully things will stay that way.

To help see what kind of wattage a given processor draws on average, we use a Kill-A-Watt that’s plugged into a power bar that’s in turn plugged into one of the wall sockets, with the test system plugged directly into that. The monitor and other components are plugged into the other socket and is not connected to the Kill-A-Watt. For our system specifications, please refer to our methodology page.

To test, the computer is first boot up and left to sit at idle for five minutes, at which point the current wattage is recorded if stable. To test for full CPU load, LinX is run with 2560MB memory usage for a total of five minutes. During that run, the highest point the wattage reaches on the meter is captured and becomes our “Max Load”.

The results here are not that surprising, with the Core i7-875K scoring close to the Core i7-870, and the Core i5-665K drawing just a bit less power than the Core i5-661. Overall, great results all around.

Final Thoughts

Intel’s K processor models are a bit interesting, from a couple of different perspectives. When AMD releases a Black Edition model, it’s clocked higher than other processors in the line-up. So, not only does someone purchase an unlocked CPU, they’re usually getting one of the fastest CPU’s the company offers.

Intel on the other hand has chosen to release K models that share identical specs to another model. So the difference isn’t faster speeds, but far more flexibility, aka: more overclocking freedom. Just how important is that freedom? Well, it depends on just how hardcore of an overclocker you are.

Earlier in the article, I mentioned that Intel hasn’t really had to release such processor models because it already dominates the CPU market from a performance standpoint, and an overclocking standpoint. The truth is, the vast majority of consumers will be pleased with the non-K models, because even those overclock like a dream. That’s been evidenced numerous times before throughout our recent content, with even budget models being able to hit 4.0GHz or higher with relative ease.

Taking away from most of the need for an unlocked processor is that typically, most users can push their CPUs to 4.0GHz speeds and beyond rather easily without stressing their memory or even BCLK all too much. Nowadays, even modest motherboards can handle 200MHz BCLK with relative ease, and at that point, most memory kits will still be well within their specced limits.

Intel Core i7 K Series Box Art Intel Core i7 K Series Box Art

It’s for that reason that K models are going to be for those who truly take overclocking seriously, and I assume that’s what Intel’s going for – those who want to break records, and need the flexibility to use whatever RAM kit they have on hand, rather than having to purchase an expensive kit, which at that point could cost more than the processor they’re overclocking with.

Regardless of whether or not K models are for the masses though is unimportant. What is important is the fact that Intel has finally broken its mold and decided to bring non-Extreme Edition unlocked processors to market, which blows the doors open to those who really appreciate overclocking, but are tired of certain limits that Intel’s recent models have imposed.

I’m sure Intel will be releasing more K models in the future, and when it does, there’s little doubt each will hold a fair premium. Whether or not that premium is worth it again boils down to how much you value overclocking. If you’re like me, and simply find a quick overclock and stick with it, then Intel’s standard models are fine. If you’re the type of person who loves tweaking for days to maximize your CPU’s performance, the K models were designed for you.

I couldn’t finish off this article without pointing out that the Core i7-875 currently is priced quite well. The i7-870 has been priced at $562 since its launch, and the i7-875K, despite being the same CPU specs-wise, costs $342.

As mentioned earlier, due to time-constraints, I haven’t been able to tweak and prod these two CPU’s as much as I’d like, so once I return home from Computex, I’ll put them through the ringer again, and if the clocks improve, I’ll update the overclocking page here, along with our related forum thread.

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