How to Overclock Sandy Bridge E to 5GHz @ Bit-Tech
Now that IDF is over and editors have had time to look over the SBE (Sandy Bridge E) info from the slide presentations you're bound to find exploritory articles speculating how to overclock future systems by reverse engineering what is presented.
For instance we already know that SBE is based on the Sandy Bridge architecture and that some of the leaked specs and board designs indicate that the LGA2011 is basically two SB chips stuck together. Of course that is an over simplification but good enough for now. One of the limitations of Sandy Bridge was the lack of real Base Clock overclocking since there was no independent system clock to control SATA and PCI Express speeds. Basically that means you run the risk of out of frequency errors as the Base Clock increased.
Based on this article they are speculating that the same Base Clock limitation exists in SBE but Intel has introducted an additional mulitplier upstream of Base Clock to further alter CPU speed.
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
In step 1 we’ve used the highest CPU divider to ‘gear down’ the desired overclock to System Clock and CPU multiplier ranges we’re confident of being able to use. In step 2 we’ve divided the result of step one by the desired System Clock – we’re still a little nervous about taking the System Clock too far from 100MHz (weirdly, we’re more nervous of this than Intel, it seems) as it’s the clock that's used by buses such as SATA and USB, and we’d rather not lose all our data.
The calculation above is using basic high school algebra to determine a Base Clock speed for a 5Ghz overclock assuming the following constants.
- Desired Speed
- Reference Clock Ratio (There appears to be two of them 1.25 and 1.66, I'm going to go out on a limb and assuming mobo makers will include more.)
- CPU Multiplier (assuming 95Mhz Bclk and the assumption that you can lower the mulitplier)
Great stuff, I can't wait to start tinkering.
Related Web URL: http://www.bit-tech.net/hardware/cpus/2011/09/20/h...
