Intel K Spec Core i7 875 and Core i5 655 Review

ccokeman - 2010-04-29 19:40:09 in CPU's
Category: CPU's
Reviewed by: ccokeman   
Reviewed on: May 27, 2010
Price: I5 655 - $216 - i7 875 - $342


Overclocking Intel processors has been strictly bclock (previously FSB) affair for quite some time with the multipliers being locked at whatever was needed to meet the rated specification of the chip. That is unless you were one of the minority that bought the top of the line Extreme Edition processors that were unlocked and may very well have been made of unobtainium based on the pricing structure of the Extreme Edition. At 1000 bucks and up (in the past) these chips were the only ones in the product stack that had "Unlocked" multipliers to allow the user the opportunity to maximize their overclock by working with both the clock multiplier and core clock speeds.In this regard the folks at AMD have really catered to the market with the Black Edition CPUs that are unlocked and sold in large quantities to satisfy a need while trying to bring in more of the market sector. Heck they even put out a Limited Edition high leakage chip called the "TWKR" to push the brand identification level higher in the overclocking community.

But I digress as this is not an article about AMD processors, but the new K-Spec unlocked CPU's from Intel, the Core i5 655 and i7 875. These "Overclocking Enabled" processors allow for added flexibility when it comes time to overclock your CPU if you are so inclined. You gain the ability to increase the multiplier without impacting memory speed or the base clock frequency of 133Mhz to reach for the limits of the processor. Now these processors are not being released tonight, but expect them to be available soon enough. Let's take them both for a spin and see how they perform in relation to the current crop of Intel's processors.

Closer Look:

These two processors arrived in the typical, non-retail packages and are clearly marked as to whats inside the little black boxes. These two processors are updates to existing packages in order to meet the needs of the enthusiast market by unlocking core clock multipliers, memory ratios and voltage options. Usually good things come in little black boxes (according to my wife anyway). So let's see if my wife's logic applies here.














First up is the Intel Core i5 655. This "Overclocking Enabled" dual core, socket 1156 processor is built using Intel's 32nm High-k second generation manufacturing process. The two cores support Intel's hyper threading technology, giving you a total of four threads that can be run simultaneously. Base clock speed for this processor comes in at 3.2Ghz. For the $40 premium ($216) over the run of the mill i5 650 ($176), you get unlocked clock multipliers, additional power options and an increase in the available memory ratios. This chip features 4MB of Intel Smart Cache, supports two channels of DDR3 memory at 1333MHz, Turbo Boost technology, as well as Intel HD Graphics or a discrete graphics package. Turbo Boost gives this processor the ability to run at an increased clock speed of up to 3.46GHz in lightly loaded situations to increase productivity when needed. This Intel processor is meant to be used in socket LGA 1156 motherboards using the Intel P55, H57 and H55 chipsets. As a dual core processor, the TDP comes in at a relatively low 73 watts.



The Core i7 875 is the unlocked and "Overclocking Enabled" step up from the i7 870 that should be a big hit with the enthusiast and overclocking crowds. Not with a big boost in clock speed, but in the availability of its unlocked bclock multipliers, memory ratios and the ability to increase the power limits on the processor. This chip is clocked at 2.93Ghz and fits right into the LGA socket 1156 motherboards already on the market. While the i5 655 is built on Intels 32nm process, the i7 875 is built using Intels 45 nm, Hi-K+metalgate process. Features on this little gem include Hyperthreading Technology that allows the four physical cores to run eight simultaneous threads and Intel Turbo Boost Technology to dynamically increase the clock speed to as high as 3.6GHz when running under the specified 95 watt power and thermal envelope. It has 8MB of shared Intel Smart Cache and supports two channels of DDR3 1333Mhz memory. The pricing on the Core i7 870 is currently $569 at popular e-tailors but this processor is to retail for only $342. That is over 200 bucks cheaper than what the top dog in the socket 1156 stable is going for.



Pretty pictures don't tell all the story, but having the ability to manipulate more options is always a good thing for the enthusiast crowd. Let's dig deeper.


Closer Look:

Included with this sample package of processors is the Intel DP55WG media series motherboard that supports both the Core i5 655 and i7 875. This motherboard is part of the Intel product line of socket 1156 motherboards and falls below the DP 55 Kingsburg Extreme Series board in its feature set. However, this is by no means a "no frills" board. This board is built upon the Intel P55 chipset and supports processors built on the LGA 1156 package and uses a two chip design. Two chips meaning the processor and P55 chipset. The packaging is purely Intel in form and function containing detailed information about the specifications and features of the DP55WG.




















The IO panel on the DP55WG contains from left to right a "Back to BIOS" switch to allow you the opportunity to reboot after a failed overclock, S/PDIF in (black) and out (gray) ports, a total of eight high speed USB 2.0 ports, a single IEEE 1394a port, a single RJ-45 Intel Pro 10/100/1000 LAN connection and last but not least the 7.1 HD sound connections. Expansion capabilities come in the form of 1-16x PCIe slot, a single 8x slot, two 1x slots and two PCI slots. Not for the gamers with multiple graphics cards, but enough for most users.



Along the bottom edge of the board there really is not a lot to discuss other than what looks to be a SATA power connection and a single USB 2.0 header. To the far right, you have a partial outline of a skull that lights from the underside. Swinging up the right side of the DP55WG, you run into most of the connections that usually populate the bottom of the board. To start, you have six SATA 3GB/s supporting RAID 0,1,5,10. Closer to the mid point, you find most of the connections you look for at the bottom of the PCB. You have the Firewire port, two more USB headers, an alternate power LED connection point, front panel infrared input and output headers and the front panel connections with the 24 pin ATX power plug just a bit further north.




Spinning around to the top of the board you have a power button and LED on the left corner, the CPU fan header and the 8 pin auxiliary power connection for the CPU. Not much along this edge but whats here is functional.



Now that the around the world tour is done, it's time to tackle the items of note on the internal surfaces. The CPU socket is of particular note in that is is not made by Foxconn. Intel is using the LOTES socket on this board. Maybe that is in response to the problem that with boards equipped with the Foxconn-manufactured sockets burning up and killing both processors and boards! It's all speculation, but it makes sense to me. Memory support comes in the form of four dimm slots capable of holding up to 16GB of DDDR3 memory in a dual channel configuration. Right under the CPU socket is the CMOS battery and a diagnostic LED that can be used to trouble shoot a failed POST attempt.




Lets see if "Overclocking Enabled" is all its cracked up to be. I'm curious to see how this new flexibility on the non Extreme Edition processors pans out.



Intel Core i5 655   
Intel Core i7 875
Number of Processor Cores
Number of Simultaneous Threads with Intel® Hyper-Threading Technology
Intel Turbo Boost Technology Frequency
Intel® Smart Cache
Processor Base Frequency
Integrated Memory Controller
Intel® Turbo Boost Technology
Number of DDR3 Memory Channels



The only way to know how a processor performs is to run it through a series of benchmarks, using both synthetic and real tasks to make a comparison as to how the processor performs against architectures from the same manufacturer, as well as competing manufacturers. Obviously, this leaves Intel and AMD at this point. To test these unlocked processors, all of the energy saving features as well as performance boosting technologies have been disabled on the motherboard in order to gain repeatable results. Otherwise, the results would not be a valid form of comparison. Intel's Turbo Boost technology provides a serious clock increase on this CPU that allows it to deliver performance in excess of what is available when the technology is disabled. A comparison will be made against both AMD processors and both the Intel socket 1366 and socket 1156 processors. Once the stock testing is completed, I will overclock the Core i7 875 and Core i5 655 to see if they deliver any overclocking headroom. Both stock and overclocked testing will be accomplished on the test platforms listed below.



Testing Setup: Intel Core i5/i7 Socket 1156


Testing Setup: Intel Core i7 Socket 1366


Testing Setup: Intel Core i5 Clarksdale Socket 1156


Testing Setup AMD Six Core:


Testing Setup AMD Six Core:


Comparison CPUs:



Overclocked settings:

The reason that these two processors exist is the flexibility of overclocking with the multiplier. Hence, that's the path I took with the testing of this pair of processors from Intel. Both chips would pull in excess of 4.6GHz for screen shots but screen shots are just that. Reliable overclocks are what I was after. Along that vein, I pushed the multiplier first to find the maximum clock speed I could run with each chip. For each one the limit really depended on how much juice I wanted to supply to that piece of silicon under the heatsink. Running the base clock at 133MHz, each chip would move well into the 30 plus range on the clock multiplier before running out of steam. Reaching the limits at around 4.5Ghz for stability with reasonable voltages on each chip, I knocked the multiplier back down and started giving the bclock an increase to really drill down the maximum, prime-stable clock speeds. The best combination of bclock and multiplier for the i5 655 was 159x28 for a final speed of 4461MHz. The 875 was a little more stubborn in this respect at 151x29 and 4392MHz. These numbers are a bit better than the 870 and about the same as I can get on the i5 661. But to do it with those chips requires you to tweak all the voltages to get there. While with the ability to work on multiplier alone, you really do not have to wring the screws off when adjusting voltages. This I feel is a good compromise for the majority of users. You can still spin the bclock to +200MHz, but with these chips you don't have to.



Intels Turbo Boost technology allow the processor to run at a higher frequency by dynamically increasing the clock speed to a higher level with no input form the user. This is done automatically as long as the BIOS is configured correctly. The maximum Turbo Boost frequency for these processors is 3.46 GHz on the i5 655 and 3.6Ghz on the i7 875. In my testing I saw maximums not quite this high and running in the 3.3+Ghz range. With these CPUs I found a nice little bonus in the BIOS. You can manually set the maximum Turbo Boost multiplier manually so that the actual boost will be more pronounced. But like anything else when pushing the limits, you need to test stability to verify that you can run the speeds you want.


Maximum Clock Speeds:

Each CPU has been tested for stability at the clock speeds listed when in an overclocked state. These clock speeds will represent the overclocked scores in the testing.




  1. Apophysis
  2. WinRAR
  3. Office 2007 Excel Number Crunch
  4. POV Ray 3.7
  5. Bibble 5
  6. Sandra XII
  7. ScienceMark 2.02
  8. Cinebench 10 & 11.5
  9. HD Tune 3.50
  1. Far Cry 2
  2. Call of Duty Modern Warfare 2
  3. Batman Arkam Asylum
  4. 3DMark Vantage


The first part of our testing will be the system specific benchmarks.


Let's get started with Apophysis. This program is used primarily to render and generate fractal flame images. We will run this benchmark with the following settings:



The measurement used is time to render, in minutes, to complete.












Lower is Better


WinRAR is a tool to archive and compress large files to a manageable size. We will use 100MB and 500MB files to test the time needed to compress these files. Time will be measured in seconds. Additionally, I will use the built in benchmark as a comparison.





Lower is Better





Lower is Better


Bibble 5:



The K-spec processors closely follow the results of the i7 870 and i5 661 in most of the testing. The overclocked speeds contributed to better scores than the standard chips.



Office 2007 Excel Big Number Crunch: This test takes a 6.2MB Microsoft Excel spreadsheet and performs about 28,000 sets of calculations that many of the most commonly used calculations in Excel. The measure of this test is how long it takes to refresh the sheet.


















Lower Is Better


POV Ray 3.7: This program features a built in benchmark that renders an image using Ray Tracing. The latest versions offer support for SMP (Symmetric Multiprocessing) enabling the workload to be spread across the cores for a quicker completion.


Higher Is Better


Geekbench 2.1 provides a comprehensive set of benchmarks engineered to quickly and accurately measure processor and memory performance. Designed to make benchmarks easy to run and easy to understand, Geekbench takes the guesswork out of producing robust and reliable benchmark results.



Again the i7 875 and i5 655 processors are performing right alongside their contemporaries. Overclocked to almost 4GHz, the i7 875 is second only to the i7 980X in most of these tests.


SiSoft Sandra is a diagnostic utility and synthetic benchmarking program. Sandra allows you to view your hardware at a higher level to be more helpful. For this benchmark, I will be running a broad spectrum of tests to gauge the performance of key functions of the CPUs.

















Processor Arithmetic




Multi-Core Efficiency




Memory Bandwidth




Memory Latency



Cache and Memory



Power Management Efficiency



The i7 875 and i5 655 both perform perform as expected, with the exception of the drop in memory scoring in the bandwidth testing.


ScienceMark tests real world performance instead of using synthetic benchmarks. For this test, we ran the benchmark suite and will use the overall score for comparison.



















Higher is Better


CineBench 10 is useful for testing your system, CPU, and OpenGL capabilities using the software program CINEMA 4D. We will be using the default tests for this benchmark.



Higher is Better


CineBench 11.5 is the latest iteration of this popular benchmark that features a new look to the interface. This test now has a simple GPU and CPU test built in.


Higher is Better


HD Tune measures disk performance to make comparisons between drives or disk controllers.



Higher is Better




Lower is Better


Throughout these tests, the K-spec processors are delivering results that are similar to the Core i7 870 and i5 661. Overclocked scores are a bit higher due to the higher clock speeds.


Far Cry 2:

Featuring a new game engine named Dunia, this game looks to be another one to stress your video card. Built especially for Far Cry 2, this engine allows for real time effects and damage. This next generation First Person Shooter comes to us from Ubisoft surprisingly - not from Crytek. The game is set in a war-torn region of Africa where there is a non-existent central government and the chaos that surrounds this type of social environment. If you have seen the movie Blood Diamond, you know the setting. Ubisoft puts the main storyline of the game into focus with these statements: "Caught between two rival factions in war-torn Africa, you are sent to take out "The Jackal," a mysterious character who has rekindled the conflict between the warlords, jeopardizing thousands of lives. In order to fulfill your mission you will have to play the factions against each other, identify and exploit their weaknesses, and neutralize their superior numbers and firepower with surprise, subversion, cunning and, of course, brute force." In this version of the game, you don't have the beautiful water, but instead the beauty and harshness of the African continent to contend with. Most games give you a set area that can be played through, while Ubisoft has given the gamer the equivalent of 50km squared of the vast African continent to explore while in pursuit of your goals. The settings used are just a few steps below the maximum in-game settings and offer a good blend of performance vs. visual quality.

















The i5 875 performed on par with the rest of the Core i7 lineup while the Core i5 655 delivered performance along the lines of that delivered by the quad core processors without Hyperthreading, namely the i5 750 and the AMD lineup.


Call of Duty: Modern Warfare 2 is the latest iteration of the venerable first-person shooter series, Call of Duty. Despite its long, successful pedigree, the game is not without substantial criticism and controversy, especially on the PC. Aside from the extremely short campaign and lack of innovation, the PC version's reception was also marred by its lack of support for user-run dedicated servers, which means no user-created maps, no mods, and no customized game modes. You're also limited to 18-player matches instead of the 64-player matches that were possible in Call of Duty 4: Modern Warfare. Despite all this, the game has been well received and the in-house IW 4.0 engine renders the maps in gorgeous detail, making it a perfect candidate for OCC benchmarking. You start off the single player missions playing as Private Allen and jump right into a serious firefight. This is the point where testing will begin. Testing will be done using actual game play with FPS measured by Fraps.


















Where the i5 655 is concerned, there is not a single resolution that it loses to even AMD's top of the line six core CPU. The i7 875 just goes and plays with the other Intel chips looking way down the ladder at the crowd of AMD chips struggling to compete. Take the GPU out of the equation and this is an all Intel field when it comes to game performance. There is a difference.


Batman: Arkham Asylum is a new game that brings together two bitter foes, The Joker and Batman. The Joker Has taken over Arkham Asylum, Gotham's home for the criminally insane. Your task is to rein the Joker back in and restore order. This game makes use of PhysX technology to create a rich environment for you to ply your trade.





















In this game, the 655 does not do as well as it did in MW2, but it still performs well against the AMD lineup. It bests all but the PII 965 and 955 when it has its clock speeds maximized. The 875? AMD does not stand a chance when compared.


Featuring all-new game tests, this benchmark is for use with Vista based systems. "There are two all-new CPU tests that have been designed around a new 'Physics and Artificial Intelligence-related computation.' CPU test two offers support for physics related hardware." There are four preset levels that correspond to specific resolutions. 'Entry' is 1024x768 progressing to 'Extreme' at 1920x1200. Of course, each preset can be modified to arrange any number of user designed testing. For our testing, I will use the four presets at all default settings.



















At the base clock frequency, the 655 has its hands full with the AMD lineup and the situation isn't much better when overclocked. The AMD PII quads just outperform it, while the Athlon lineup delivers slightly less grunt. The 875 at stock and overclocked speeds is still a powerhouse delivering performance that the AMD group does not come close to.


Earlier I made a reference to good things coming in little black boxes and wanting to know if my wife's philosophy carries any weight. The short answer is an emphatic yes. (I hate it when she's right). The rest of the answer is that Intel is now knocking on the door that AMD has been trying to close for a while with its Black Edition processors. No longer does the high performance Intel crowd have to pony up and spend a grand for the ability to maximize your clock speeds. Granted this is the socket 1156 lineup instead of the 1366 platform, but you capture a broader audience by hitting the more economical platform. At a retail price of $216, the i5 655 is going to cost you a premium over the i5 650, but to some, the extra features may be worth it. Now with the i7 875, Intel has done an "about face" with this processor. The i7 870 currently retails for $569 at many of the most popular e-tailors. The price point for a chip that is basically identical but is unlocked, will be selling for a mere $342. A price difference of $217. That's just huge. The $342 price is a price premium of about 60 dollars over the cost of a lower clocked i7 860, so the choice is clear.

These processors are unlocked and meant to be overclocked. This is why both processors reached in excess of 4.5GHz for screen shots and between 4392MHz (i7 875) and 4461MHz (i5 655) for prime 95 stability. This however, took some work to get accomplished as both would easily get close to, or over the maximum clock speeds with just the use of the multiplier for overclocking. In order to really get as high as possible, multiplier and bclock tweaking was required. The benefit is that you really do not have to hit all the ancillary voltages nearly as hard as when you have to push the bclock to reach your final overclock.

All things considered, I think Intel has a winning proposition with the introduction of these processors to the market. They offer a flexibility in overclocking that was in the past reserved for the biggest (and most expensive) dog on the block in Intel's lineup. They come in at a reasonable price point and overclock like stink. If a socket 1156 rig is in your future, then the i7 875 should be the processor for you.