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Overclocking Ivy Bridge: Core i7-3770K Is A Mixed Bag

Intel Core i7-3770K Review: A Small Step Up For Ivy Bridge
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It’s easy to assume that shifting down to 22 nm lithography makes the Ivy Bridge design a more receptive platform for overclocking. Although it packs more transistors into less space, increasing density, the fact that the highest-end parts sport 77 W TDPs suggest lower thermal output.

At the same time, the 22 nm node is brand new, and Intel proudly admits that it changed more of its design than it normally would heading into a die shrink. That could spell trouble.

So, while it’s unclear how much truth is behind early reports that Ivy Bridge-based processors aren’t overclocking well, our own experiences in the lab certainly indicate a lack of consistency. Between three editors currently working with Core i7-3770K CPUs, two are able to hit 4.7 GHz and one saw frequencies as high as 4.9 GHz on air and using BIOS-specified voltages between 1.3 and 1.35 V. Curiously, though they seem to run Prime95 and Linpack without protest for hours on end, certain applications in our benchmark suite (mainly, 3ds Max) take these chips down within seconds. Achieving stability required dropping to 4.5, 4.5, and 4.77 GHz on our three samples.

In comparison, my boxed Core i7-2700K loads to Windows at 4.8 GHz and runs solidly at 4.7 GHz at 1.35 V.

The main difference between overclocking these two architectures, aside from Ivy Bridge appearing comfortable at just slightly slower frequencies, is that Intel’s 22 nm-based chips also run significantly warmer (somewhere around 10°C higher at each CPU’s maximum stable overclock). Thus, overclockers using big air will likely have the most difficult time nailing settings that are suitably aggressive, but still modest enough to promote longevity.


Ivy Bridge
Sandy Bridge-E
Sandy Bridge
Core Ratio Multipliers
Up to 63x
Up to 57x
Up to 59 x
Real-Time Core Ratio Changes
Yes
All Cores Simultaneously
No
Integrated Graphics Ratio Multipliers
Up to 60x
N/A
Up to 57x
Real-Time Graphics Ratio Changes
Yes
N/A
No
DDR Ratio/Frequency
Up to DDR3-2667
Up to DDR3-2400
Up to DDR3-2133
DDR Granularity
200/266 MT/s
266 MT/s
266 MT/s
XMP Reference Code
v.1.3
v.1.2 or 1.3
v.1.2
BCLK Overclocking
Limited
1.0/1.25/1.67x Straps
Limited


The phase/dry ice/LN2 crowd is in a different position. Enthusiasts able to keep Ivy Bridge cold have already exceeded 6.9 GHz with four cores active, partly because Intel increased Sandy Bridge’s 59x maximum core ratio to 63x. Because Z77 suffers the same limited BCLK headroom as Z68 and P67, most reports put 107 or 108 MHz as the practical limit. But boards able to hit 110 or 111 MHz couple well with higher multipliers and extreme cooling.

What can you expect from a Core i7-3770K at 4.5 GHz compared to a Core i7-2700K at 4.7 GHz? Nearly exactly the same performance, it turns out. Though I’m not entirely certain you’d want to leave the -3770K running with one core at 88 degrees for very long, it is stable.

In 3ds Max, which is very well threaded, overclocked Ivy Bridge finishes our workload just two seconds faster, narrowing a five-second gap at stock clock rates. iTunes puts the two chips just one second apart. At 3.5 GHz, they’re separated by three seconds.

Consider this a cursory look at overclocked performance in single- and multi-threaded tests. Our German team is working on a more in-depth overclocking analysis that should go live sometime this week.

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