Hardware Intel Core i7 Build: Overclocking the Intel DP55KG and Core i7 860


This is the third post documenting my upgrade to an Intel Core i7 Lynnfield system. In my first post I discussed the components I selected and why. I talked about assembling the system and some of the challenges I encountered in my second post, and in this final post I’ll be discussing my efforts at overclocking the Intel DP55KG motherboard and Core i7 860 processor.

Two Approaches

Intel’s new “Turbo Mode” feature is able to increase the processor multiplier value beyond its default value (21 in the case of the Core i7 860) if the processor is operating within what it considers are safe temperature parameters. For example, in Intel’s Core i7 Bloomfield architecture, processors are allowed to raise the stock multiplier value by 1 or 2 depending on the number of cores being used. Intel’s Lynnfield processors are considerably more aggressive with Turbo Mode, increasing Turbo Mode multipliers within a range of ~2-5. Essentially what this means is that when fewer processor cores are demanded by an application or process, larger multiplier values are used, thus the processor is allowed to run faster than the default multiplier would normally allow. In the case of the Core i7 860, it’s not uncommon, for example, to see it use a multiplier value of 26 in single-threaded applications, yielding a processor speed of 3.46 GHz, well above its stock speed of 2.8 GHz. While this sort of dynamic overclocking is pretty damn impressive, a question arose for me when it came time to overclock my Intel DP55KG and Core i7 860: should I attempt to overclock the system with Turbo Mode enabled, meaning I would have to consider the headroom required when higher multiplier values are used, or should I simply disable it and go with the more traditional overclocking approach? I ended up trying both approaches to see how they compared and to evaluate which would work best for me.

Regardless of which approach you use though, overclocking a Lynnfield system is pretty straight forward. Adjust the host clock frequency until the system achieves a stable CPU speed. From there, the memory multiplier can be adjusted to compensate for the change in host frequency. If desired/needed you can also adjust the CPU voltage, memory voltage, and Uncore voltage to further stabilize the system. That’s pretty much all the adjusting the architecture allows you to do.

    Turbo Mode enabled

My first attempt at overlocking the Intel DP55KG and the Core i7 860 involved raising the host clock frequency but leaving with Turbo Mode enabled. These are the BIOS settings I started with:


Host Clock Frequency Override: Manual

Performance -> Processor Overrides

CPU Voltage Override Type: Dynamic
CPU Voltage Override: Default (default)
CPU Idle State: High Performance
Intel Turbo Boost Technology: Enabled (default)

Performance -> Memory Configuration

Performance Memory Profiles: Manual – User Defined
Memory Multiplier: 12
Memory Voltage: 1.65
Uncore Voltage Override: 1.10 (default)

Performance -> Bus Overrides

All settings in this section were left at their default values.


Enhanced Intel SpeedStep Tech: Enabled (default)
CPU C State: Enabled (default)

With this approach, my objective was to try to achieve the best stable overclock I could using Turbo Boost and leaving the voltage settings at thier default values. However, I did alter two voltage settings: the CPU Voltage Override Type, which I set to Dynamic, allowing the CPU to still manage its own power usuage but with higher upper limits; and the Memory Voltage, which I set to 1.65 to match the voltage input specified for my Mushkin DDR3-1600 kits. I left the RAM timings at the default SPD values of 9 9 9 24.

And the result? I was able to achieve a host clock frequency of 154 MHz before the system became unstable (stability in this case is defined as the ability for the system to run without failure using Prime95 (v25.9) Large FFT for 2-3 hours). This yielded a CPU speed of 4 GHz, assuming a Turbo Boost multiplier of 26 (154 * 26 = 4.00 GHz). I did notice, however, that the multiplier in my case generally liked to stay at 25 a large percentage of the time during idle. I suspect this was the result of the High Performance setting in BIOS that forces the system to use the higher multiplier when the operating system would otherwise be allowed to lower it.

According to CPU-Z (v1.53) The CPU voltage (VID) fluxuates between .8 and .9 at idle and core temperatures according to Speedfan (v4.40) were ~30c at idle. Given the DRAM multiplier setting of 12, the DRAM frequency weighed in at a nice 1848 MHz. Loading all four cores resulted in VID rising to 1.096 volts and core temperatures to ~63c. Using all four cores of course also resulted in the system using the default CPU multiplier value of 21 (154 * 21 = 3.23 GHz).

So, in summary, I was able to achieve ~15% overclock under load using Turbo Boost and leaving the voltage settings at thier default values.

    Turbo mode disabled

After determining the optimal overlocking settings for my Intel DP55KG and the Core i7 860 using default voltages and Turbo Mode enabled, I attempted to overclock the system with Turbo Burst disabled as well as the freedom to use higher voltage settings, if necessary, to make the system stable. These are the BIOS settings I started with:


Failsafe Watchdog: Enable (default)
Host Clock Frequency Override: Manual
Host Clock Frequency: 133

Performance -> Processor Overrides

CPU Voltage Override Type: Static
CPU Voltage Override: Default (default)
CPU Idle State: High Performance
Intel Turbo Boost Technology: Disabled

Performance -> Memory Configuration

Performance Memory Profiles: Manual – User Defined
Memory Multiplier: 10
Memory Voltage: 1.65
Uncore Voltage Override: 1.10 (default)

Performance -> Bus Overrides

All settings in this section were left at their default values.


Enhanced Intel SpeedStep Tech: Disabled
CPU C State: Disabled

And the result? With Turbo Burst disabled and the latitude to increase VID and other voltage settings if necessary, I was able to achieve a host clock frequency of 170 MHz using a VID of 1.2 before the system became unstable, yielding a CPU speed of 3.5 GHz (170 * 21 = 3.57 GHz). Further increases in VID, memory or Uncore voltage did not allow for a stable system using higher clock speeds. Core temperatures rose to ~35c at idle and loading all four cores caused the core temperatures to rise to ~74c. With a the DRAM multiplier setting of 10 instead of 12, the DRAM frequency fell to 1700 MHz. Here again I left the RAM timings at the default SPD values of 9 9 9 24. I did try to run with the DRAM multiplier set at 12 but there was just no way my 1600 MHz RAM was going to run at 2040 MHz!

So, in summary, I was able to achieve ~28% overclock by shutting down Turbo Boost and raising VID to 1.2.


Afterwards, I threw a few highly unscientific tests at both cases to see how they compared. The first involved transcoding a typical MPEG-2 DVD *iso to the h.264 high-profile format using Handbrake. There was no significant difference in time between the two methods, however both represented a nice improvement over the default settings. Turbo Boost, however, did provide a nice bump in memory bandwidth, due mostly to the ability to run at a higher DRAM multiplier value. The use of Turbo Boost also won out when running 3DMark Vantage, suggesting that the higher multipler values played a role. The game-based tests I ran were essentially useless since the particular games I had on hand to test with (BattleForge, Crysis, and X3 Terran Conflict) more strongly rely on the GPU for performance improvement and not the CPU.


Turbo Mode is something that should be evaluated based on your needs and the specifics of your overclock. Which one did I go with? I decided to run with Turbo Mode enabled and the lower host clock frequency. There were a couple of reasons for this choice. First, I rather like using the default voltage settings; by allowing Intel to manage the power settings, I’m able to run my system moderately faster, and in some cases a hell of a lot faster, but also a lot cooler. Second, I typically run applications that do not utilize all four cores, so a moderate overclock with Turbo Mode gives me better results than a higher-speed overclock without Turbo Mode. However, it’s good to know that as I grow to depend on more cores consistently, I can simply shutdown Turbo Boost and clock the system higher.

Tags: ,

17 Responses to “Intel Core i7 Build: Overclocking the Intel DP55KG and Core i7 860”

  1. Matt in L.A. Says:

    Excellent review of the overclocking potential of the 860. I recently purchased this processor and I have been doing reconnaissance of various tech sites to get a feel for overclocking this CPU at stock voltages before I start my build. Your methodology is sound and your writing prose translates the subject information clearly.

    After reading your article, I feel that I have finally found a reasonable arguement for leaving “Turbo Mode” enabled and my forthcoming build will benefit from your research. That said, I would also love to see a comparison of running the 860 with and without Hyperthreading enabled. To me, that is just as important as your research on Turbo Mode on/Turbo Mode off.

    Good work my man. I look forward to coming back to your site more often :-)

  2. iceflatline Says:

    Thanks for the kind words Matt. Great suggestion regarding Hyperthreading. I’ll post another comment with the results when I can find the time to test it. If you happen to get it done before I do please let me know what you find.

  3. KumaN Says:

    Hi there iceflatline,

    Just a note on X3:TC – it’s a single-threaded game(well theres another thread for sound processing, but it’s probably less than 10% of overall load) unfortunately, and due to CPU/OS limitations, although it seams that it’s somewhat using all cores(25%-30% each roughly) it’s just the OS “passing” the thread through all cores in a round ribbon fashion. That applies to all single threaded apps unfortunately, and if the process sticks to one core or is passed between them it doesn’t make much difference(but AMD was going to introduce a countermeasure to it in Bulldozer, so if it will happen that gives us hope until programmers at Microsoft will learn how to handle this(and I’m afraid that before they do it will be way too late ;-) ) ). You can easily check if an application benifits from multi-cores by using affinity setting in task manager(right click on process).

    That’s all I guess ;-) (it’s just I’m playing X3 on a 2.8Ghz C2Q…gimmie a 4,5Ghz dualcore! ;-D )

  4. iceflatline Says:

    KumaN, Excellent! Good info…

  5. Kyale Says:

    Thank you for testing the turbo feature and sharing your results. So many accounts over look it.

  6. iceflatline Says:

    You’re welcome Kyale, thanks for commenting.

  7. IanL Says:

    Wish I had found this last month, it would have helped me greatly. I am running a 875k on a dp55kg and going through the same oc cycle. I believe that ocing with turbo enabled is better. You can play with the BCLK to better match ram settings for stability, and then use turbo offsets for increased cpu speed.I did find that regarding HT on/off, when off you can achieve a higher cpu speed at a lower temp.

  8. iceflatline Says:

    Thanks for your comments IanL. Admittedly, I dismissed HT as having a significant affect one way the other. You’ve peaked my curiosity now :)

  9. IanL Says:

    Just a quick note on HT
    When I set all of my cores to run at 4.1 Ghz, prime 95 would crap on 5 threads within 45 min to an hour. I also reached 75-80 degrees, a little to warm for my liking as I am only running a Noctua cooler. With HT off, Prime 95 lasted over two hours and the temps never went above 73c. As I dont know which apps take advantage of more than two cores and or hyperthreading, I have set my system to run 1 core at 4.27, 2-cores at 4.0, 3-cores at 3.9, and 4-cores at 3.87. with HT on. Prime 95 has run for 13 hours and max temp so far is 74c. My next test is to turn off HT and see how far the temps drop.

  10. iceflatline Says:

    IanL, good stuff. Yeah, differently let me know if/how dropping HT affects your temps. Also, how do you like Noctua coolers overall?

  11. IanL Says:

    I like it. I am using the NH-D14 in a AMTEC 300 case. I ran the fan controls outside the case so i could access them without removing the side panel. All of my tests were in slow mode which is whisper quiet. If i use high mode you can hear the fans but you get an additional 1-2 degree temp drop. I was lucky as my ram is low profile and the first two slots clear the radiators just fine. Not sure if 4×1 high end ram will fit without removing the heat spreaders though. All in all it works great. As I am an electrical engineer i have a hard time with the idea of water coolers. I think running 4.0 Ghz on air is just fine. Going higher would require a different cooling system but I believe you reach the point of diminishing returns. If your looking for benchmarks i guess it would be ok. For normal use why spend hundreds more for a less than 5% gain. The new games rely on a good GPU more than a fast cpu anyway. Sorry about the rambling.

  12. iceflatline Says:

    Awesome. I really like Noctua coolers but none of them looked like they were going to clear the heat spreaders on the Mushkin RAM I had already purchased. So, I ended up going with the Cooler Master Hyper 212. It’s certainly not going to help me set in OC records but for the moderate amount I’m doing it’s more than adequate.

  13. IanL Says:

    As you are/were a fan of Asus, what do you think of the P7H57D-V-EVO MB. I bought one to try because it not only unlocks the turbo multipliers, but also the BCLK multiplier. In addition you get one IDE interface ,USB 3.0, and it supports ram bandwith up ti 2133 (they claim). Do you know of any benefits The H57 chipset has over the P55 other than onboard video support??

    Also, I am checking with Noctua to see if there is a listing of high end ram that mounts with their cooler.

  14. iceflatline Says:

    That looks like a nice board. Other than that the H57 provides Intel HD video support when using a Core i3 5xx or i5 6xx CPU, video support seems to be the only major difference that I can see.

  15. IanL Says:

    Well I turned of HT and prime 95 has run for 9 hours so far with a max temp of 68c. With fans in high mode that could drop to 66- 67 if everything stays together. Will see in another 4 hours.

  16. iceflatline Says:


  17. IanL Says:

    Well, prime95 ran for 16 hours with HT turned off and temps stayed at 68c. Turned the fans on high and after an hour temps only dropped 1 degree. Next is to attempt 1-core at 4.4, 2-core at 4.27, 3-core at 4.0 and 4-core at 3.9. Not sure how high the temps will go with the vcore increase as I dont want to exceed 75c, as this will give me a little overhead. Once I see how far I can go and stay within a self imposed thermal envelope and run stable. (For me stable is running prime95 for 12 hours or so) I will then run my tests again raising the BCLK and dropping the multipliers. At the very least I will begin to understand the relationship between all of the variables involved in the game of overclocking.

Leave a Reply