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One Step Towards Overclockers

The most interesting thing about the new platform is not the processor specifications or chipset functionality, but the aspects that make LGA 2011 so appealing for overclockers. LGA 1155 wasn’t so attractive for overclocking fans. It turned out unable to allow overclocking processors by simply raising the BCLK frequency, which has immediately affected the number of overclocker systems built around Sandy Bridge. In fact, you had to have an unlocked processor, like Core i5-2500K or Core i7-2600K, to succeed. The moment first complaints about that started coming in, the company officials immediately responded that the users shouldn’t get too worried at this point because the upcoming LGA 2011 will be specifically designed for overclocking and will meet all their needs in time.

Now we finally saw what the new Intel platform for overclockers looks like.

Well, we have already seen from the processor specifications that two out of three models will have an unlocked multiplier, which will allow simple straight-forward overclocking. However, even a locked Core i7-3820 model will also be overclockable. Intel promises that the options allowing to increase the BCLK frequency will now work in a much trickier manner.

In fact, the old problems will not go anywhere. Just like on LGA 1155 platforms, PEG and DMI frequencies will be tied up to the base clock frequency generator, i.e. even a slight increase in Reference Clock will cause the same problems as with current Sandy Bridge. The good news is that in LGA 2011 systems the BCLK frequency will be additionally multiplied by an intermediate reference clock ratio multiplier before getting to the processor, and this multiplier will be at 1.0x, 1.25x or 1.67x. In other words, besides the traditional processor clock frequency multiplier, there will be an additional intermediate overclocking multiplier that will serve for overclocking by adjusting the “bus frequency” outside the CPU. This multiplier will raise the base clock of the processor and its functional units (including the memory controller), but leave it untouched for the I/O part. Moreover, this multiplier will exist for any LGA 2011 processors, even the ones with the locked multiplier. And frankly speaking, it doesn’t even belong to the CPU, as it is the chipset that is responsible for its operation. It means that it cannot possibly be locked in a processor.

As a result, we will no longer use the following traditional formula for the processor frequency:

[CPU Frequency] = [CPU Multiplier] x [Reference Clock].

Instead we will use the following one:

[CPU Frequency] = [CPU Multiplier] x [Reference Clock Ratio] x [Reference Clock],

where [Reference Clock Ratio] is this particular additional multiplier of 1.0x, 1.25x or 1.67x.

This little trick will allow overclocking LGA 2011 processors even without changing its actual multiplier at all. Just like in LGA 1155 systems, we can only adjust the reference clock slightly without losing any of the performance. In reality it means that when the BCLK frequency changes by ±5%, the system may become non-operational. But the additional reference clock ratio multiplier will allow us to send 125 or even 167 MHz frequency to the processor without changing the BCLK at all. This way both birds will be killed with one stone. The CPU will work as if it received 125 or 167 MHz base clock, while in reality DMI and PCI Express will be working at BCLK frequency of 100 MHz.

Moreover, LGA 2011 system will also allow memory overclocking, just like the LGA 1155 systems do. The nominal supported memory is the same DDR3-1067/1333, but with a 266 MHz increment you will be able to reach DDR3-2133 or even DDR3-2400. By the way, LGA 2011 platforms will support the new XMP version 1.3, which is intended specifically for four-channel memory with the frequency of 1866 MHz or higher.

In order to achieve stability during overclocking of an LGA 2011 system, we should be able to change three voltage settings: Vcore, Vmem and system agent voltage.

Intel shared with us some of their overclocking success. They used a boxed water-cooler, which we are going to discuss a little later in this review. Although it can’t boast better cooling efficiency than a high-performance air-cooler, the Core i7-3960X processor overclocked to 4.75 GHz.

By the way, I would like to draw your attention to the fact that this is a very unusual overclocking for Sandy Bridge, but it confirms everything we have just said above. This system uses 95 MHz reference clock. However, at the same time it also uses the additional Reference Clock Ratio of 1.25x. As a result, the processor received “modified” bus frequency of 119 MHz. Taking into account the 40x multiplier, the processor frequency comes to 4.754 GHz. This is how tricky it is :)

The memory in this case works as DDR3-2218 and the Reference Clock Ration of 1.25x also applies to it, because the system originally has DDR3-1866 mode set it in by default. You can check out the voltages and timings on the photo above.

And the next image shows the actual system that was used for all these overclocking experiments.

Overclocking to 4.75 GHz, performed by Intel specialists, doesn’t strike you as something super-natural. So, it turns out that Sandy Bridge-E processors for LGA 2011 will overclock pretty much as good as the existing Sandy Bridge processors for LGA 1155. However, we didn’t expect anything different here, because nothing has actually changed in the production process as well as microarchitecture. Only the number of cores has increased and so did the TDP. This means you might want to consider getting a better cooler, but it is not a reason enough to assume that the new LGA 2011 processors should be more or less overclockable.

 
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