2-Chip Solution

Intel has developed a new chip structure which they are beginning to implement with the 5 series chipset. The old structure which required 3 chips (CPU + GMCH + ICH) is being replaced with just a 2 chip layout (CPU+PCH) – the PCH standing for Platform Controller Hub.

Here’s a simplified diagram of the new solution:

The new Platform Controller Hubs have many more functions and so are much more complicated than previous Southbridges. As I mentioned before, DMI is used for communication between the CPU and PCH.

Although DMI has a max bandwidth of 2GB/s much fewer than the QPI up at 25.6GB/s, there is no need to worry as there shouldn’t be too much data to be transferred between the chips – supposedly.

Overclocking

Overclocking follows a similar pattern to that of the LGA1366/i7 with perhaps the only notable difference being that the base clock is equal to the QPI frequency – note that I doubt you will find the QPI mentioned anywhere in the BIOS.

With Turbo Boost enabled, we successfully booted the i5-750 at 4.0GHz using a BLCK frequency of 190 and a multiplier of 21. To achieve this, we had to use the following voltages: Vcore of 1.44V, IMC of 1.3V and a CPU PLL voltage of 1.9V.

During stability testing using Large FTTs on Prime95, the temperatures did get into the “dangerous” category at around 90 degrees. However, this was due to only having the Cooler Master TX3 CPU Cooler. It is essentially a low-end cooler and not intended for high overclocking and unfortunately we didn’t have time to mod a larger LGA1366 cooler to the i5-750.

Click to enlarge

Therefore, we believe that the processor would have gone higher with the cooler being the limiting factor due to the temperatures. Also, from past experience with the i7 overclocking, the Turbo boost seems to limit the overclocking of the BLCK frequency.

Therefore, for multi-threaded applications it would be wise to disable the Turbo Boost as it essentially used for single threaded processes allowing the multiplier to go up to a maximum of 24 for one core. The multiplier drops down for every extra core added though so a max of 23 for dual cores and right down to 21 (shown in our overclock) when utilising all cores.