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Overclocking Haswell: You’ll Pay For That

The Core i7-4770K Review: Haswell Is Faster; Desktop Enthusiasts Yawn
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If you purchase one of the two K-series parts in Intel’s Haswell-based portfolio (and you have a Z87-based motherboard), you’ll have access to the same knobs and dials that were available from the Core i7-3770K and i5-3570K, with one notable change: the BCLK ratios popularized by X79 Express are back, facilitating some manipulation of the number that gets multiplied against the clock ratio. Intel exposes 1.0x, 1.25x, 1.67x, and 2.5x straps.

There’s a colossal difference between what Haswell-based LGA 1150 processors can do in theory, and what they can do after Intel’s product guys get done disabling the bits and pieces to create a differentiated stack, though.

Overclockers maintain control over core frequency using ratios up to 80x in 100 MHz increments. The on-die graphics engine is also adjustable in 50 MHz increments via ratios as high as 60x. Further, the memory controller is technically unlocked, allowing options for 200 and 266 MHz steps with a logical ceiling at 2,933 MT/s. Finally, the platform controller hub’s clock generator is unlocked too, supporting frequencies as high as 200 MHz.

But as with generations past, there remains a relationship between the DMI clock and PCI Express clocks—and you want PCI Express to stay as close to 100 MHz as possible. So, Intel implements 5:5, 5:4, 5:3, and 5:2 ratios to maintain constant PCIe clocks with a variable BCLK. Unlike the LGA 2011 platform, which used the CPU to adjust those ratios, Haswell requests this from the PCH. The outcome is similar, though. Expect a useable range between 5-7% around the ratio you choose for fine-tuning your overclock.

That’d all be well and good if Intel was enabling this new level of flexibility for the folks who don’t spend extra on K-series parts, giving them the ability to pick higher BCLK settings without access to the ratio multiplier. However, the company instead chooses to restrict the ratios to the Core i7-4770K and i5-4670K—the same ones you can already overclock in 100 MHz increments. Anyone buying one of the 11 other SKUs in Intel’s new Core i7 and i5 line-up is out of luck.

Overclocking Core i7-4770K

Moving on, what can you expect from a Core i7-4770K, in terms of overclocking headroom? We have a couple in the lab, and are getting 4.7 GHz, at most, across all cores using Prime95 to test for stability. However, those samples come from Intel. We were much more interested in feedback from someone with many, many retail parts at their disposal.

Our first-hand information involves a high double-digit number of processors, including samples and final shipping boxed CPUs. Sort testing was limited to 1.2 V to keep heat manageable. Ring/cache ratios are pegged at 3.9 GHz, with the memory controller operating at 1,333 MT/s. Of the chips available for sorting, only one is stable at 4.6 GHz under full load. A few are capable of operating at 4.5 GHz. More run stably at 4.4 GHz. Most are solid at 4.3 GHz and down. As you stretch above a 1,600 MT/s memory data rate or a ring ratio to match your highest single-core Turbo Boost ratio (which helps maximize performance), your top stable core frequency tends to drop.

Load-line calibration has very little, if any, effect with Haswell. There’s simply less flexibility to coax a killer overclock out of one of these CPUs using levers that were popular previously. Although the most enthusiast-friendly motherboards still include pages of options, a number of them simply don’t do anything beneficial. Flatly, it sounds like engineers and enthusiasts alike are still trying to figure out what the more obscure settings actually do.

We’re going to have to accept that Haswell-based parts get hotter, faster, it sounds like, and that they might fall a few hundred megahertz short of comparable Ivy Bridge-based parts with conventional cooling methods. It’s a good thing, then, that the architecture is inherently faster to help compensate.

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  • 1 Hide
    phil_livesey , 1 June 2013 16:56
    Yet another competition not open to UK residents, despite this being on the UK site. Thankyou Tomshardware!!!!
  • 0 Hide
    Pailin , 1 June 2013 18:06
    Sounds... disappointing after hearing about the Uber high LN OCs.
    Also thought I recently heard somewhere of others getting Nice 5GHz+ OC's on water and Very low vcore's - perhaps you guys have a Poor batch?
  • 0 Hide
    das_stig , 1 June 2013 19:46
    So once again, the UK site publicises a competition as part of a review and once again, it's limited to the US readers. Come on TH tis just sucks and shows that you don't give a toss about the rest of the world. The internet is a global community, it doesn't stop at the US border. Surely your programming monkies can code a conditional statement to blockout content if outside the U.S of Ass or are they to busy coding up more ad boxes ????
  • 0 Hide
    daglesj , 1 June 2013 21:01
    Guys, you are posting this on the useless and superfluous UK version.
    No one will be reading it.
  • 0 Hide
    mi1ez , 2 June 2013 11:01
    Quote:
    the only arrangement emerging today is the quad-core SoC

    SoC is pushing it a bit given it doesn't contain RAM, USB, network, etc.
  • 0 Hide
    bwrlane , 2 June 2013 14:08
    Great article, but what a let down. Ivy Bridge was already a disappointment, but Haswell is far more disappointing even than that. My 2700k based PC can manage 4.84GHz under full load, while remaining stable. My 3770k PC can do 4.74GHz. The IPC improvements are almost exactly compensated for by the lower attainable clock speed.
    But with Haswell, the world has gone backwards. Apparently, a 4770k can be pushed to 4.4GHz and that's it. That's a 7% reduction in clock speed. Since most benchmarks don't show a 7% improvement at stock, Haswell is slower than the Ivy Bridge that it replaced.
    For years we've been hearing that the answer to all our tech questions is "you have to wait for Haswell for that". But as this article shows, that was a lot of hot air.
  • 0 Hide
    doive1231 , 2 June 2013 19:33
    What a load of baloney we were spun about Haswell graphics. I read it would be a real step change and we should expect something special. Well, the comparisons between HD4000 and HD4600 are a real kick in the teeth. Nothing more that a few frames per second in most tests. Bah, Intel. And not I won't be getting Crystalwell.
  • 0 Hide
    selfmade_exe , 2 June 2013 21:45
    amd trinity gets bottlenecked by 1600 ram!!!
  • 0 Hide
    JRAtk94 , 2 June 2013 23:42
    Yay for AMD.
    Finally, AMD wins on price AND performance.
  • 0 Hide
    selfmade_exe , 3 June 2013 22:22
    TO ALL THOSE RESPONSIBLE FOR THIS TEST: I DARE YOU "CLEVER" TESTERS TO TEST AMD TRINITY WITH 1866 RAM OR ABOVE, AND ALSO COMPARE WITH RICHLANT FLAGSHIP. ALSO, PLZ RUN GPU_CAPS_VIEWER -> THE JULIA SET WITH GPU OPENCL AND COMPARE WITH TRINITY! PERIOD!
  • 0 Hide
    Tedfoo25 , 5 June 2013 08:34
    I'm quite impressed actually. With a decent overclock, you are essentially getting a 3930k on the cheap with a socket that will have CPUs developed for it in the future.
  • 0 Hide
    mateau , 11 June 2013 15:22
    Haswell is old tech already. AMD just rekeased FX-9590 a 5 ghz 8 core MONSTER that is sure to stomp all over Hasbeen. And the FX-950 is unlocked for overclocking!!!!!
  • 0 Hide
    Alps , 11 June 2013 19:26
    "several strides behind"?? I'll but an AMD FX-8350 and overclock it, thanks for the usual biased review!!
  • 0 Hide
    Alps , 11 June 2013 19:26
    "several strides behind"?? I'll but an AMD FX-8350 and overclock it, thanks for the usual biased review!!
  • 0 Hide
    Alps , 11 June 2013 19:26
    "several strides behind"?? I'll but an AMD FX-8350 and overclock it, thanks for the usual biased review!!
  • 0 Hide
    Alps , 11 June 2013 19:26
    "several strides behind"?? I'll but an AMD FX-8350 and overclock it, thanks for the usual biased review!!
  • 0 Hide
    Alps , 11 June 2013 19:29
    "several strides behind"?? I'll but an AMD FX-8350 and overclock it, THANKS for the usual BIASED review!!
  • -1 Hide
    genz , 16 June 2013 19:49
    Why are we comparing a dual module CPU to a quad core/8 thread one? Shouldn't you be using the quad module/8 core AMD chip?
  • 0 Hide
    genz , 16 June 2013 19:49
    Why are we comparing a dual module CPU to a quad core/8 thread one? Shouldn't you be using the quad module/8 core AMD chip?
  • -1 Hide
    genz , 16 June 2013 19:51
    Why are we comparing a dual module CPU to a quad core/8 thread one? Shouldn't you be using the quad module/8 core AMD chip?