So, basically there are two BCLK multipliers available: 1,25x and 1,66x. The BCLK overclocking capabilities seem to be slightly better too (95.1MHz BCLK -> 115MHz BCLK?), which would bring us 95-140MHz and 160-190MHz ranges to play with. All-in-all, it seems that the OC finetuning capabilities are back with these chips; the only question that remains is whether or not the clock walls. are still present.
Without an unlocked multiplier on an LGA1155 system, you’re limited to Base Clock overclocking, which Intel only recommends increasing by up to 5 per cent, while others claim it’s only good for up to a 10 per cent boost.
Thankfully, we now know that Sandy Bridge E systems support more flexible Base Clock overclocking than Sandy Bridge systems. The key is a new divider between the Base Clock of the system and the CPU – it’s a gearing mechanism, just like a memory strap or a CPU multiplier. There are two dividers to tweak, at 1.25x and 1.66x, with both acting to gear up the Base Clock used by the CPU, while leaving the Base Clock for the rest of the system alone. Having two Base Clocks in one system will probably get confusing, though, so in the absence of clear labelling from Intel we’ll call them the System Clock and the CPU clock.
You’ll also need to tinker with the Turbo Boost tweaks with which you're familiar when overclocking a Sandy Bridge system – increasing the maximum possible power draw of the CPU to prevent Turbo Boost capping your overclock, or reducing it during a prolonged session.
Let’s say we’re aiming for an overclock of 5GHz (something that the Intel engineers said they had achieved during a bit of mucking around in their office). We don’t know how much of an overclock that is, but we know that 50x100MHz=5GHz. However, if we have a ‘locked’ Sandy Bridge E CPU that doesn’t have a multiplier of 50 or more, we’ll have to change the System Clock and the CPU divider instead. The maths requires us to work backwards from 5GHz like this:
- 1) 5,000 ÷ 1.66 = 3,012
- 2) 3,012 ÷ 100 = 30.012
- 3) 3,012 ÷ 30 = 100.4