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Overclocking

System Builder Marathon, Dec. 2009: $2,500 Performance PC
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Completely opposite of the $2,500 machine’s ease of assembly was the difficulty of its overclock, calling into question our choice of a Core i7-860 processor and a mid-priced motherboard.

The problem was heat. We did a great amount of testing on this particular Core i7-860 processor and found that it could actually exceed the overclocking capability of the Core i7-870 used in our P55-UD4P motherboard review.  However, the i7-860 also converted 10% more power into heat (330W compared to 300W) at 1.45V core and full load. We thus needed more cooling.

Unfortunately, we also found that the Xigmatek HDT-S1284 cooler produced similar temperatures at 270W as our reference cooler produced at 300W. Further inspection of the HDT-S1284 revealed several potential design problems, including a low-speed fan that couldn’t be increased regardless of its PWM-control capabilities, a sink that leaked most of that fan’s air from the side, leaving the center of its fins almost unused, and an add-on installation kit that provided little contact pressure. We tried resetting the fan several times but got our best results (a drop of nearly two degrees Celsius) by simply pressing down against the sink’s top.

Given a 10% higher thermal load and 10% less cooling capability, we weren’t going to get anywhere close to the processor’s limit at our chosen voltage. Our new limit would be 1.35V, with 4.0 GHz and a full CPU load of eight Prime95 threads pushing the CPU to 90 degrees Celsius.

We then encountered a second heat issue: at full GPU load, the graphics cards would pump too much heat into the case. This would have made it impossible to load both the CPU and GPU simultaneously, a condition we certainly lament.

Using a BIOS setting of 1.30625V with load-line calibration enabled, our CPU would climb to 1.312V but only clock to 3.65 GHz stably, with both the CPU and GPU cores at full load.

Knowing that the system could potentially support even higher clock speeds when only one or two threads were enabled, we also tried getting to this point using Intel Turbo Boost. A base clock of 162 MHz got us to 3.56 GHz with for cores loaded, 4.05 GHz with two cores active, and 4.2 GHz with a single core active, while the slightly lower four-core results yielded to better average performance thanks to how many of our benchmarks are single- or dual-threaded. An added benefit was lower idle power, since Intel’s power-savings features must be activated in order to reach the highest Turbo Boost ratios. Yet this turned out not to be the perfect solution we’d hoped for, as core voltage occasionally didn’t increase fast enough at program launch to keep the system stable. Our demands for perfect system stability forced us to revert to old-fashioned low-efficiency overclocking methods.

Our RAM was capable of reaching the same DDR3-1600 CAS 8-7-7-18 timings as the previous set, but only when a fan was over it. That could be partly due to P55-UD4P BIOS increments of 0.02V, which forced us to set 1.66V rather than 1.65V, but it’s also true that this month’s $2,500 machine lacks the accessory fan used in September. To keep things cool, we decreased DRAM voltage to 1.64V, a drop that along with the slight increase in clock speed, forced us to use looser 8-8-8-18 timings.

Our graphics card BIOS limits GPU overclocking to 900 MHz. DRAM restrictions were more adequate, allowing us to reach the memory’s stable 1,270 MHz limit. We know that these cards could go much faster using unlocked BIOS and another manufacturer’s Afterburner Utility, but we didn’t want to void the graphics warranty of this future giveaway system by flashing non-native card BIOS.

Tuners interested in copying these efforts (or using them as a baseline) can view BIOS screenshots by clicking on the above thumbnail images.

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  • 0 Hide
    ionut19 , 23 December 2009 01:25
    ...!
  • 0 Hide
    Crashman , 23 December 2009 08:23
    ionut19...!


    Hello ionut19! You probably just did the same thing as me and, like me, got redirected to the .uk site where the comments section is currently empty?
  • 1 Hide
    LePhuronn , 23 December 2009 19:26
    Something strikes me as a little weird on that system. Don't know what it is. Dunno, for a budget of $2,500 I would've thought you could've gotten a bit more.

    GPB equivalent from Overclockers UK: £1,709.85

    Matching budget I did a X58 version for £1,703.87:
    i7 920
    Asus P6T SE
    6GB Corsair XMS3 1600MHz CAS8
    2x Sapphire 5870
    2x SpinPoint F3 1TB
    Cogage True Spirit
    Corsair HX850
    LG BH08LS20 BD-RE
    Antec 902

    which is pretty much the same system to be honest. £75 exchanged the SpinPoint RAID for 1 SpinPoint F3 and a Samsung PB22-J 64GB SSD. Dropping the Blu-Ray burner to the equivalent LG Blu-Ray ROM would bring the system back under budget.

    Maybe it's because just because I personally favour X58 over P55.
  • 0 Hide
    Crashman , 23 December 2009 19:53
    LePhuronnSomething strikes me as a little weird on that system. Don't know what it is. Dunno, for a budget of $2,500 I would've thought you could've gotten a bit more.GPB equivalent from Overclockers UK: £1,709.85Matching budget I did a X58 version for £1,703.87:i7 920Asus P6T SE6GB Corsair XMS3 1600MHz CAS82x Sapphire 58702x SpinPoint F3 1TBCogage True SpiritCorsair HX850LG BH08LS20 BD-REAntec 902which is pretty much the same system to be honest. £75 exchanged the SpinPoint RAID for 1 SpinPoint F3 and a Samsung PB22-J 64GB SSD. Dropping the Blu-Ray burner to the equivalent LG Blu-Ray ROM would bring the system back under budget.Maybe it's because just because I personally favour X58 over P55.


    So did the builder, but the P55 was used anyway in hopes of a better overclock on the newer CPU. That didn't work out. But anyway...the RAM was good RAM, for a good price, and it ran at over 1600 CAS 8 anyway. Now if that same cost-savings eye would have been put into a few other places, perhaps X58 and a big enough liquid cooler to chase that big overclock could have been purchased.
  • 0 Hide
    LePhuronn , 23 December 2009 20:02
    Crashmanbig enough liquid cooler to chase that big overclock could have been purchased.


    That Cogage will easily cool the i7 920 up to 4GHz on its own, past that you'd need a good chip to exceed 4.2GHz anyway. And a better motherboard too perhaps.
  • 0 Hide
    Crashman , 23 December 2009 20:10
    LePhuronnThat Cogage will easily cool the i7 920 up to 4GHz on its own, past that you'd need a good chip to exceed 4.2GHz anyway. And a better motherboard too perhaps.


    Well, the i7-860 in the review would go to around 4.4 GHz on a huge air cooler with super-fast fans, but those weren't included in the purchase and were only used in diagnosing the O/C problems. You can get a 920 to 4.20 on a 2x120mm radiator.
  • 0 Hide
    sghndubh , 27 December 2009 09:29
    So I read the "uncompromising compromise" conclusion page ( http://www.tomshardware.co.uk/build-new-pc,review-31758-16.html# ) and it seems like a lot of the build changes.

    Using the original build as a basis, and the improvements that were suggested on the compromises page, what should I fit? If I bumped my budget up to $2750, would that help?

    Any advice would be appreciated!
  • 0 Hide
    daglesj , 28 December 2009 00:38
    This should be called the "more money than sense" system.
  • 1 Hide
    LePhuronn , 28 December 2009 01:42
    daglesjThis should be called the "more money than sense" system.


    Hardly. This is about standard for a high-end gaming system.

    More money than sense would have 3 5870s, Core i7 975 OC'ed to 4.2GHz, 12GB Corsair Dominator GT 2000MHz, 3 Intel 64GB Extreme SSDs in RAID 0 for system and water cool the lot.