Confused CPU/RAM i7

As far as the voltage is concerned, there are 2 main voltage sets you need to deal with in an modern Intel platform. There is the CPU voltage (set) and the memory voltage (singular).

All memories are rated for some specific voltage, with a JEDEC standard of 1.5V for nominal voltage, and 1.35V for low voltage (also DDR3L), there are also lower voltages like 1.25V and even lower, but I'm not sure if those are standard voltages for desktop use (although you CAN get 1.25V sticks for desktop). For Ivy Bridge and Sandy Bridge CPUs, the absolute max WAS stated to be 1.65V, because beyond this, the transistors degrade rapidly in the memory controller, which is onboard the CPU. Since a lot of motherboards have a voltage tolerance that isn't tight, getting 1.65V memory for an Ivy Bridge is risky, because although you set the voltage at 1.65V in the BIOS, the actual voltage could be, say 1.70V when measured with a meter. I would recommend (and you can gather by looking at memory specifications) that unless you have a specific need for super-fast RAM, stick to what the fastest is, at 1.5V. If you don't use the onboard GPU on a modern CPU (Ivy B or AMD's APUs), you don't need to necessarily go above 1600 Mhz to get all the performance benefits. BUT, for the ease of future upgrades and some OC room, I would recommend 2133 Mhz or 1866 Mhz RAM (the fastest ones you can get while keeping RAM voltage at 1.5V). Higher speed RAM also have higher compatibility issues, for example, DDR3 at 3000 Mhz (VERY FEW of these exist) are reputed to work on 1 in 10 Ivy B systems.

The CPU voltage actually consists of a few different voltages (or voltage planes) on modern CPUs, like the memory controller/PCI-E hub/etc which might use its own voltage, the CPU cores (which might even have voltage per core), the cache, etc, etc. On an Intel (or AMD) platform, you can increase the memory controller voltage (small adjustments are safe) to support higher speed memory, to allow the memory controller to "pump"/"charge" the memory in a smaller unit of time (since the clocks are ticking faster on a faster set of RAM). From Xbitlabs:

"Our experiments suggest that high-speed memory modes are perfectly functional and do not even require any tricks like fine-tuning secondary voltages. For example, it only took a small (by a mere 50 millivolts) increase in memory controller voltage for our Ivy Bridge CPU to work faultlessly with DDR3-2667 SDRAM."

These are the different voltage planes on an Ivy Bridge CPU:



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NOW, as for the BCLK clock, it is a Master clock of sorts on an Intel platform. This means that nearly all other functions on the board that requires a clock to strap to (sync to, latch on to, or phase-lock on to), will be strapped to the BCLK. Usually as a rule of thumb, if you are overclocking the BCLK, plan on being able to get about nominally 5% before you start seeing weird issues. Although the CPU might be perfectly stable at higher BCLKs, the rest of the system (USB controllers, SATA controllers, etc) may start to have issues. A higher BCLK typically causes other onboard components to have problems, since those components are not usually overclocked/overclockable and are made with rather small clock margins. This is about how much (maximal) you'll be able to get from BCLK, although for stable day to day use (and Win8 is particularly picky about the BCLK), I'd recommend less than this OC:



Taken from Tom's roundup of boards:

http://www.tomshardware.com/reviews/z77-express-ivy-bridge-benchmark,3254-34.html