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Haswell-E Overclocking

There are usually some overclocking-related innovations in each new Intel platform. After the company had taken to catering to the overclocking community, we got a lot of interesting overclocking features over the past few years. But the developer’s creativity seems to have dried out, because the Haswell-E and the LGA2011-v3 platform have the same overclocking capabilities as the LGA1150. We have no problem with that, though. Unlocked Haswell-based CPUs can be overclocked quickly and easily.

The only obstacle to reaching high clock rates with them is the low-efficiency thermal interface between the processor’s cap and die but the Haswell-E connects the heat-spreading cap and the die with fluxless soldering using indium-based solder which features very high thermal conductivity. Thus, Haswell-E CPUs are going to be a real treat for enthusiasts who have got fed up with the overheat issues of regular Haswell-based products.

Theoretically, overclocking a Core i7-5960X, Core i7-5930K or Core i7-5820K goes like this. Each of these CPUs has fully unlocked frequency multipliers and lets you adjust their Turbo Boost settings. The maximum multiplier value has been increased since the Ivy Bridge-E and equals 80x.

The CPU-integrated voltage regulator supports flexible voltage adjustment for the processor’s x86 cores and other subunits. All popular voltage adjustment methods can be used: static, offset and adaptive.

Besides overclocking via the frequency multiplier, you can increase the base clock rate. The LGA2011-v3 platform has a standard set of PCI Express and DMI frequency divisors that let you easily use a base clock rate of 100, 125, 166 and 250 MHz. Most Haswell-E CPUs will only work at the first three values, though. You can deviate from them, but the clock rate of the PCI Express and DMI buses becomes nonstandard in this case, which quickly renders your computer unstable. Stability is only ensured when the base clock rate is less than 5% off the core values of 100, 125 and 166 MHz.

The memory controller integrated into the new processors allows overclocking DDR4 SDRAM in the same way as DDR3 could be overclocked on the earlier platforms. The memory frequency can be set with a step of 200 or 266 MHz. New memory modules support XMP 2.0 profiles which may contain settings that go beyond the JEDEC specs.

Talking about our practical tests, we first tried to overclock the flagship Core i7-5960X Extreme Edition. Frankly speaking, we didn’t expect it to overclock much because it had eight cores and a rather low standard clock rate. However, the low default voltage gave us some room for increasing it whereas the efficient internal thermal interface prevented overheat.

Using a liquid cooling system Corsair Hydro Series H110, we made our Core i7-5960X Extreme Edition stable at a clock rate of 4.2 GHz. We raised its voltage to 1.3 volts without overheat. During a stability check with LinX 0.6.5, the peak temperature was 96°C (the Haswell-E enables thermal throttling at 105°C).

Although the resulting clock rate doesn’t look high, our speed gain is quite substantial. The 8-core Haswell-E turns out to be able to reach the same frequencies as the quad-core Haswell models for the LGA1150 platform. The default clock rate being 3.0 GHz, the frequency increase is as high as 40%. And we’re talking about a flagship CPU and sustainable overclocking (you can run the CPU at such settings for as long as you want without any problems). So if it were not for its steep price of $1000, the Core i7-5960X would be easily the most demanded CPU for enthusiasts.

As for the six-core Haswell-E models, their overclockability isn’t that impressive. Our Core i7-5930K couldn't reach the clock rates of the earlier Ivy Bridge-E CPUs. It looks like Intel indeed makes these 6-core processors out of defective 8-core ones, which affects their overclocking potential. So our sample was stable at 4.2 GHz, just like its senior 8-core cousin. To ensure stability, we had to increase its voltage to 1.3 volts, and the CPU cores were as hot as 97°C when running LinX 0.6.5.

Thus, our Core i7-5930K could speed up by 20% above its default clock rate.

The lack of overclocking prowess of the new 6-core CPUs is confirmed by the results of the Core i7-5820K. Although it did better than its cousins, its performance was far from impressive. It reached 4.3 GHz, which was a mere 100 MHz higher than the peak clock rate of the flagship Core i7-5960X. Like with the other two models, we had to increase the voltage to 1.3 volts. The temperature was up to 95°C during a LinX 0.6.5 stability test.

It turns out that all Haswell-E processors, irrespective of the number of their x86 cores, have the same frequency potential: up to 4.2 or 4.3 GHz. Of course, we mean such overclocking that can be utilized on a 24/7 basis. Anyway, our Haswell-E processors do not overclock as smoothly as their Sandy Bridge-E and Ivy Bridge-E predecessors that could reach 4.5 GHz and higher. And this is not caused by a poor thermal interface or anything. It is the Haswell design itself that prevents better overclocking. Multi-core Haswell-based processors get much hotter than older CPUs as their clock rate gets higher.

It doesn’t mean that an overclocked Haswell-E is going to be slower than an overclocked Ivy Bridge-E, though. The more advanced microarchitecture and the sheer number of x86 cores should make the Core i7-5960X, Core i7-5930K and Core i7-5820K faster. You’ll see this in our performance tests where we’ll benchmark them at their default settings as well as in overclocked mode.

Testbed and Methods

It is reasonable to compare the new Haswell-E processors and the entire LGA2011-v3 platform with their predecessors: Ivy Bridge-E and LGA2011. That’s exactly what we’re going to do in our today’s tests. We do not include the quad-core i7-4820K, however, just because it is obviously inferior to the new 6- and 8-core models. Instead, we will test a configuration with a Core i7-4790K (Devil’s Canyon series) which also has only four cores but features a high clock rate (well above 4 GHz) to make up for that.

Considering that the Haswell-E series is offered for enthusiasts, the senior and junior models are going to be tested at their default clock rates as well as in overclocked mode (as described in the previous section of our review). To make the picture complete we’ll pit them against a flagship Ivy Bridge-E model (Core i7-4960X) overclocked to 4.5 GHz and a Devil’s Canyon processor working at the same clock rate.

Considering the market positioning of the LGA2011-v3 platform, we’ve introduced some changes into our graphics subsystem. It consists of two AMD Radeon 290X cards working in CrossFireX mode. This will help us get more interesting results in games where the graphics subsystem wouldn’t serve as a bottleneck anymore. Moreover, we’ll be able to see the benefits of senior Haswell-E models which allow building multi-GPU configurations with graphics slots working as PCIe x16/x16.

Below is the full list of hardware components we used in our testbed.

  • Processors:
    • Intel Core i7-5960X Extreme Edition (Haswell-E, 8 cores + HT, 3.0-3.5 GHz, 20MB L3 cache)
    • Intel Core i7-5930K (Haswell-E, 6 cores + HT, 3.5-3.7 GHz, 15MB L3 cache)
    • Intel Core i7-5820K (Haswell-E, 6 cores + HT, 3.3-3.6 GHz, 15MB L3 cache)
    • Intel Core i7-4960X Extreme Edition (Ivy Bridge-E, 6 cores + HT, 3.6-4.0 GHz, 15MB L3 cache)
    • Intel Core i7-4960K (Ivy Bridge-E, 6 cores + HT, 3.4-3.9 GHz, 15MB L3 cache)
    • Intel Core i7-4790K (Haswell Refresh, 4 cores + HT, 4.0-4.4 GHz, 8MB L3 cache)
  • CPU cooler: Liquid cooling system Corsair Hydro Series H110
  • Mainboards:
    • ASUS X99-Deluxe (LGA2011-v3, Intel X99)
    • ASUS Z97-Pro (LGA1150, Intel Z97)
    • Gigabyte X79-UP4 (LGA2011, Intel X79)
  • System memory:
    • 2x8GB G.Skill [TridentX] F3-2133C9D-16GTX DDR3-2133 SDRAM (9-11-11-31)
    • 4x4GB G.Skill [TridentX] F3-2133C9Q-16GTX DDR3-2133 SDRAM (9-11-11-31)
    • 4x4GB Corsair Vengeance LPX CMK16GX4M4A2666C16 DDR4-2666 SDRAM (15-17-17-35)
  • Graphics cards: 2x AMD Radeon R9 290X (Hawaii XT, 4 GB/512-bit GDDR5, 1000/5000 MHz) in CrossFireX mode
  • Storage: Intel SSD 520 240GB (SSDSC2CW240A3K5)
  • Power supply: Corsair AX1200i (80 Plus Platinum, 1200 W)

We carry out our tests in Microsoft Windows 8.1 Professional x64 with the following drivers:

  • AMD Catalyst Software Suite 14.9
  • Intel Chipset Driver 10.0.17
  • Intel Management Engine Driver
  • Intel Rapid Storage Technology

As we’ve written above, some of the CPUs are tested twice: at their default clock rates and in overclocked mode.

  • Intel Core i7-5960X Extreme Edition at a clock rate of 4.2 GHz and voltage of 1.3 volts
  • Intel Core i7-5960K at a clock rate of 4.3 GHz and voltage of 1.3 volts
  • Intel Core i7-4960X Extreme Edition at a clock rate of 4.5 GHz and voltage of 1.5 volts
  • Intel Core i7-4790K at a clock rate of 4.5 GHz and voltage of 1.225 volts
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