System bus

QPI or Quick Path Interconnect is the Intel communication path between the CPU and the X58 chipset on the motherboard. So all devices not controlled on the CPU die itself have to communicate with the CPU via the QPI. For instance, the memory controller in built into the CPU, so the memory bandwidth is not limited by the QPI, it has it’s own direct link to the CPU. However, the PCIe controller is located on the X58 chipset, all of your storage devices, NICs, audio devices, USB devices, etc….they all have to communicate with the CPU via the QPI.

The good news here is that Intel created the QPI for CPU to CPU communications for use in multi CPU servers for the enterprise market. That means the bandwidth they built in is HUGE, and in reference to overclocking, higher QPI speeds don’t affect performance enough to notice in day to day activities. So I NEVER run the QPI beyond x32, with the bclock at 200MHz this would result in the QPI running at 6.4GHz which is plenty for anything you might throw at it.

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