At IDF 2011, Intel revealed that Ivy Bridge would have a higher maximum CPU multiplier of 63X (up from 59X on Sandy Bridge), an up to 60X multiplier for the IGP, support for memory speeds up to DDR3-2800, and smaller 200MHz memory speed increments.
One of the really cool new features is dynamic overclocking, which allows users to change the CPU/IGP multipliers without rebooting. It worked flawlessly when using Intel's Extreme Tuning Utility (XTU). Overclocking an Ivy Bridge system is going to be identical as on Sandy Bridge, so you will want to buy an unlocked K-series processors if you want to increase the clock frequency in any significant way. We really don't expect to see any chips with a maximum postable multiplier lower than 50X, so that's already than on Sandy Bridge, but as you will see below that's really not the big concern this time around.
As you can see above, we managed to achieve a stable 4.8GHz core clock with about 1.35V. For comparison, we got 4.75GHz with 1.45V on our i7-3870, while our i7-2600K needed about 1.42V to hit 4.70GHz stable.
Ivy Bridge overclocks very well, generally better than mainstream Sandy Bridge at every voltage point up to 1.35V. Above that? We don't know. We don't know because we were told by an always reliable third-party that stress testing above 1.35V is a risk with IVB due to potential degradation, but we also don't know because we were scared that it would cause a house fire...
To put it simply, we think that the term "blazing hell inferno" might be short-selling Ivy Bridge's heat problem once you cross a certain threshold. Past 1.30-1.35V temperatures skyrocket, so we're going to recommend that everyone on air-cooling, even high-end air-cooling, stay in the 1.25V-1.30V range. Most chips shouldn't have any problems hitting 4.5GHz with 1.20V or less, which is awesome for your average casual overclocker, but scaling gets progressively worse as you go above these levels.
Our overclock was stable, we threw every app we could at it and had four 2-3 hour gaming sessions, but we aren't going to hide the fact that during the one hour AIDA64 stress test at least one core hit a truly absurd 101°C, while the others routinely reached into the 90's. At least that proves that these new chips are resilient to short-term heat.
It’s pretty clear to us that Intel is using very low leakage transistors with IVB, and when you combine extremely high transistor density with a die that has half the surface area of Sandy Bridge, the temperature situation gets out of control quickly when overvolting. Although our chip is an engineering sample sample, we know for a fact that retail chips will feature similar heat characteristics. We don’t think that it’s outside the realm of possibility that Intel might release a new stepping in 6-9 months, or at least that later chips might just be tuned for higher leakage as the manufacturing process improves, as was the case with the Bloomfield D0 stepping.
As mentioned above, degradation is a concern with these chips if you use too much voltage, so for stability testing we're going to recommend that cautious users switch over from IBT/LinX/Prime95 to the AIDA64 stress test or OCCT 4.2.0, both of which provide a much more realistic/real-world type of load on the processor.
With regard to power consumption, using the above overclock our system idled at 61W and topped out at 205W under the full load of Prime 95 In-place large FFTs. For comparison sake, our Core i7-2600 at 4.6Ghz with 1.42V had identical idle numbers, but higher 221W load numbers. This is actually a pretty decent result for IVB, it is certainly a heck of a lot better than the Bulldozer FX-8150 debacle, which when overclocked to 4.6GHz at 1.50V idled at 195W and pulled an immense 550W when running Prime 95.
On the BCLK side of things we didn't notice any great leap forward either. Our result was just a little bit better than the 105MHz (without the Gear Ratio, of course) with hit on the Core i7-3820 and the 107MHz on the Core i7-2600K. It's all a coin flip though. Except for maybe the sub-zero crowd, voltage and heat considerations are going to be way more of a limiting factor than the BCLK on Ivy Bridge.
Intel's been pretty cocky with regard to touting the frequency headroom of the HD Graphics 4000 IGP, and sure enough we were able to achieve a lofty 39% overclock / 1.6GHz frequency with relatively little additional voltage (+0.223V). The associated performance gains were very impressive indeed, and would have been even more so had we jacked up the memory frequency instead of keeping it at stock.
Given the fact that Intel’s own documentation advised us to use up to +0.440V, we expect to see some insane numbers from those with a little better cooling and a lot more courage than us.
On the memory front we didn’t really set any new records since our 16GB G.Skill DDR3-2133 kit really doesn’t like anything above DDR3-2220 without an unhealthy boost in voltage. Having said, the Ivy Bridge/Z77 platform is absolutely amazing when it comes to memory clocking. Records are already being set, and there's a bunch of insane DDR3-2600/2800 32GB kits around the corner.
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