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Intel K series relieve CPU multiplier limitation-Core i7-875K OC performance Review


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Intel has launched LGA 1156 structure around 1 year, and the CPU product line is also plenty.

If we divided into Chipset, P55 is mainly for Core i5-750/Core i7-860 and 870.

They are 4C/4T or 4C/8T structure, more CPU Cores, better performance and ATX form factor MB.

Another 2 chipset are H55/H57. H57 is not popular due to its high price.

H55 is mainly for All In One. The CPU built-in GPU is the new design.

Main CPU product line has Core i3-5X0/Core i5-6X0 2 series, and they are 2C/4T Cores mainly.


Of course, both series CPU can be installed with P55/H55.

But P55 has no VGA output function, you still need external VGA with Core i3-5X0/Core i5-6X0.

Core i5-750/Core i7-860、870 CPU don’t built-in GPU. Even install in H55still need external VGA.

Users need to understand the LGA 1156 features you need to pay attention to.


Normally, Intel has un-locked CPU known as Extreme Edition.

The price usually is around 999USD. The models are LGA 1336 Core i7 965/975/980X.

Or LGA 775 platform has QX6850/QX9775. The models above are Intel Extreme Edition un-locked CPU.

LGA 1156 hasn’t seen this segment CPU since launched.

Intel finally launched 2 LGA 1156 Unlock CPU on 6/1.

The code is Core i7-875K for P55 MB and Core i5-655K for H55/H57 MB.

LGA 1156 platform unlock CPU called K series.


This review is about Intel Core i7-875K

Clock is 2.93GHz, supports Turbo Boost can reach 3.6GHz performance.

Physical 4 Cores with Hyper-Threading, total can achieve 8 threads named 4C/8T.

45nm manufacturing, 8MB L3 Cache and it’s all top spec in LGA 1156.



Core i7-875K back can see the difference in every version and design.



MB is GIGABYTE P55A-UD4P, which is hi-end P55 design and spec.

The price is around 7000NTD. In P55 market, it’s mid-high end market position.



Smart Dual LAN, 3X USB Power, On/Off Charge port.

The features above are GIGABYTE main technology for UD4P.



Support SATA3 and ATI CrossFireX



Provide CPU 12-phase PWM, and 2-phase for memory.




CPU: Intel Core i7-875K



VGA: ATI Radeon HD 5830

HD: Intel X25-V 40GB RAID 0

POWER: be quiet! power4 DELUXE 530W

Cooler: Mega Shadow Deluxe Edition

OS: Windows7 Ultimate 64bit



Default Setting

CPU 133.2 X 24 => 3197.8MHz

DDR3 1598.8 CL6 6-6-24 1T


Hyper PI 32M X8=> 18m 33.250s

CPUMARK 99=> 496



CrystalMark 2004R3 => 236739




CPU => 5.44 pts

CPU(Single Core) => 1.08 pts


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PCMark Vantage => 15310



Core i7-875K already has very high performance at default clock as with Turbo Boost OC technology.

As per CPU utilization rate, the clock will be in between 2.93~3.60GHz. It should be affordable for most application.


Sandra Memory Bandwidth - 19460 MB/s

EVEREST Memory Read - 14717 MB/s



Even though LGA 1156 has dual channel structure, not like as triple channel in LGA 1366, so the DDR3 bandwidth is lower.

Core i7 CPU built-in Memory Controller design makes LGA1156 DDR3 bandwidth be higher than dual channel PC platform over 1.5 times more.


PSU is be quiet! latest power4 DELUXE 530W which is high C/P value product.

100% Japanese solid capacitors, 12cm low acoustic fan, 2-way 12V output designs.



In this CPU Core i7-875K and VGA HD5830 platform, it can adequate OC or high loading system.

530W is also enough for ATI CrossFireX



3D Performance

3DMark Vantage => P14430

CPU SCORE => 19866

GPU SCORE => 13224



StreetFighter IV Benchmark

1920 X 1200 => 168.64FPS




1280 X 1024 => 146.92/131.13/182.86/100.72 fps






3D gaming performance is relied on VGA capability.

However, the higher performance CPU can enhance 3D performance around 10-20%.

Core i7-875K performance is quite high standard, so when you use with ATI HD5380 for better 3D.



Stnadby - 37~40



CPU Full Load - 53~59

Intel Burn Test v2.4,Stress Level Maximum



Under room temperature is 28℃, CPU full speed is still lower than 60℃.

For 4C/8T spec, Core i7-875K temperature is very good.

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Power Consumption

Standby - 141W



CPU Full Load - 217W



CPU standby and full load power consumption difference is 76W. The difference is still in acceptable range.

The standby is 141W, but most power consumption is by hi-end VGA...


HDD Test

Using Intel mainstream version SSD, X25-V 40GB, for RAID 0



X25-V 40GB official spec is reading 170 MB/s and writing 35 MB/s



HD Tune Pro 4.01 Benchmark Average 355.9 MB/s,Access Time 0.1ms

ATTO DISK Benchmark over 128k test can achieve 392 MB/s for reading and 89 MB/s for writing.

CrystalDiskMark - 390.8 Mb/s for reading and 86.74 MB/s for writing.



FDEBENCH test result is 327.6 Mb/s for reading and 89.8 MB/s for writing.



X25-V 40GB spec is lower performance than X25-M 80GB, reading 250 MB/s and writing 70 MB/s.

However, I recommend users can buy X25-V 40GB for RAID 0. The cost is similar and the RAID0 capacity is 80GB also.

Also, X25-V RAID 0 performance can reach over 320~350 MB/s for reading and writing is similar with X25-M, is above 80 MB/s.

This combo is better than buy just one X25-M 80GB. 4K, writing performance, is also the special strength of Intel SSD.


OC Performance

First of all, you can refer to my BIOS fine tune set up for 200/2000

BIOS Main page





Core i7-875K ratio range : X9~X62



DDR3 Setup


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Voltage setup page



CPU Feature



If you want to pull high CPU/DRAM frequency, you need to fine tune QPI/Vtt Voltage base on each CPU capability.

If you enable Hyper-Threading to let CPU be 4C/8T, the CPU Voltage also depends on its capability.

During test, Core i7-875K OC voltage is very well.

200/2000 at 4.2GHz only need QPI/Vtt Voltage 1.210V and CPU Vcore 1.3000~1.32500V to be stable for all test.



CPU 200 X 21 => 4200MHz

DDR3 2000 CL8 8-8-24 1T


Hyper PI 32M X8=> 14m 28.968s

CPUMARK 99=> 653



CrystalMark 2004R3 => 297430




CPU => 7.17 pts

CPU(Single Core) => 1.43 pts



PCMark Vantage => 17389



As OC Core i7-875K to 4.2GHz, the performance increases around 20~30%.

The stabilized voltage only needs 1.296V~1.328V.

It’s really excellent and can show how mature for Intel CPU manufacture is.


Sandra Memory Bandwidth - 24460 MB/s

EVEREST Memory Read - 19253 MB/s



DDR3 bandwidth is also very high after OC.

Overall DDR3 performance increases around 25~30%. It’s very close to LGA 1366.


3D Performance

3DMark Vantage => P16431

CPU SCORE => 25766

GPU SCORE => 14660



StreetFighter IV Benchmark

1920 X 1200 => 181.90FPS




1280 X 1024 => 157.43/142.07/192.42/110.61 fps


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As the different 3D benchmark software, the score has 5~15% higher.

4.2GHz Core i7-875K has better performance as running 3D software.



Standby - 43~37



CPU Full Speed - 71~89

Intel Burn Test v2.4,Stress Level Maximum



As OC to 4.2GHz, it also needs to raise the voltage quite much.

So you can see the temperature is high as running at full speed. This is the price for OC by air cooling.


Power Consumption

Standby - 172W



CPU Full Speed - 339W



Power consumption result is similar with temperature. It’s almost same in standby but raise a lot in full speed mode.

4.2GHz standby and full speed difference is 167W. It’s more than 2 times more.


Finally, pull clock to 4508MHz and make CPU-Z certificate.



windwithme OC Intel Core i7-875K 4.5GHz Certified


Even if you pull the CPU voltage, CPU clock still can be higher but may not be able to pass the burning test and cannot use for long time.

I prefer to OC the system under air cooling and can be stable. It will be more useful for most users.


Intel Core i7-875K current price is around 11700NTD, about 363USD.

The previous top LGA 1156 is Core i7-870 and the price is 19000NTD, around 589USD.

The channel has off shelf the Core i7-870 and replace by 875K which is higher C/P value.

You can see Intel top LGA 1156 CPU price drop to let user pay less for buying.


The price of 875K and 860 are very close.

875K is also unlock, so the C/P is not lower than 860.

If you are planning to buy Core i7-860, you can also consider Core i7-875K.


Most user worry about the OC needs to have good capability of MB and DDR3, so they give up in the beginning.

The unlock 875K make OC be easier. The user only need to set the ratio and voltage.

I do hope Intel can have more SKU than 875K/655K. They also can consider to have more entry LGA 1156 CPU for choosing. :)

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