Test System

BIOS Setup, Putting It All Together

Getting down to overclocking is actually a whole lot easier than it first appears. However, there are a few critical areas you need to look at right from the start to maximize the potential overclock. The most important part is checking those voltages I listed earlier. Writing them down so you can view them easily later is important because you are going to enter all of those values into the BIOS MANUALLY before overclocking. I cannot stress this enough. YOU MUST DO ALL OVERCLOCKING MANUALLY. A big part of controlling heat issues is keeping all voltages at their lowest possible values, but automatic settings with many motherboards make maximum COMPATIBILITY the priority. This COMPATIBILITY focus includes setting voltage values a bit higher than they need to be for quite a few chips, since the silicon quality between CPU samples of the same model is still quite varied. Expect your board to set some if not all values at levels much higher than needed if you don't take control to keep those voltages in check.

Secondly, since most of us will be using a discrete GPU, disabling the onboard GPU, if your BIOS allows it, is another big exercise in heat control. Having the iGPU disabled prior to installing the OS can lead to temperature reductions of up to 30°C over having it enabled for even only Intel QuickSync usage, so you definitely want to disable it to get the most out of the CPU.


Voltage tuning is actually pretty simple. Once manual settings are applied to all sections of the chip, you can play with the voltages for CPU, cache, and memory, and independently increase their multipliers. BCLK overclocking increases the complexity a fair bit, but most chips should be able to use the 125 MHz divider with stock voltages. If you have a board that only supports offset voltage tuning, setting the minimal voltage offset is the easiest way to get everything as close as possible to the default values. Some motherboards have minimum voltage values that are higher than what some CPUs require at stock when manual voltage-tuning options are enabled (I'm looking at you, ASUS!). Using the Offset Mode function for initial testing can in such a case be a very good idea.

Going by guides given to me by Intel and other board makers, the five main CPU voltages—CPU, cache, System Agent, Analog I/O, and Digital I/O—are all safe at up to 1.3 V. Intel does, however, recommend increasing voltages by no more than 10%, which falls slightly under the maximum domain values given in those guides. For example, since the maximum "stock" CPU voltage is 1.15 V according to Intel, an increase of 10% would give us 1.265 V, which is really close to the recommended maximum cited in ASUS-based guides that have been posted by various websites over the past weeks. Cache gets the same treatment, so rough maximum values are generally the same. The further away from those maximum values your chip is at stock, the better of an overclock you should be able to get. Chips with a stock core voltage of 1.050 V and under should be capable of 4500 MHz or more at around or just above that 1.265 V value. Chips with a cache voltage of 1.050 V should see a maximum cache multiplier of "42" or so for long-term use, though I personally feel "42" to be more than enough. Intel did not offer the option to independently set cache speed without it somehow having an impact.

Specifically memory overclocking requires a mix of VCCSA, VCCAIO, and VCCDIO voltages. For clocking at up to 2800 MHz, many chips will need no increases to anything other than the VCCSA. The other two I/O voltages become more important with my retail CPU samples as VCCSA reaches over 1.100 V, and all three are critical when increasing the BCLK, but keeping them as low as possible while maintaining stability is the best course of action overall.

For direct values to use under custom water-cooling, I suggest 1.265 V on the CPU, 1.15V on cache, 1.05V on VCCSA, VCCAIO, and VCCDIO (with up to 2400 MHz using a 4x 4GB kit). You should not need to go over 1.865 V on the FIVR setting either, and going over 1.9 V can quickly destroy some chips when combined with a few other settings, so be especially careful with it. Being able to run ALL of those voltages at the highest safe value without throttling is going to depend on your individual chip and the cooling solution you use. I suggest forcing the multiplier for CPU cache to "39" and if your BIOS supports it, also adjusting the minimum cache multiplier to "8" when going for long-term use. This will allow cache speed to increase with the workload, which prevents excess heat, but it is also best to keep the cache multiplier at a static value for stability testing. These are the general voltage ranges I test every motherboard at, provided the options are there, and so far, it has proven successful for the many different motherboards I've already reviewed, assuming your CPU's stock voltage is 1.05 V or less. I did have one chip with a stock voltage of 1.070 V, and it was truly disappointing. When adding memory overclocking to already high CPU clocks, increasing VCCSA, VCCAIO, and VCCDIO can be critical to booting your CPU with some of the higher dividers, even with a default BCLK value. Other chips will, on the other hand, require no boosts to those voltages at all—all the way up to the 2933 MHz divider, which is currently the maximum working value you can pick. That said, overclocking is obviously not just about simply changing settings—you also need to test those settings.