Intel Corp (INTC)

[ChipGeek]

I think comparing Quickpath to PCI-e is asking the wrong question.

For one thing, Quickpath was never meant to replace PCIe, it was meant to replace the FSB, whose bandwidth does not scale with multiple cores.

What's clouding the picture is that the system bus in single-socket systems will be going away soon, as more and more gets integrated into the CPU socket (I often hear nowadays the CPU socket being referred to as a system 'black hole', continually sucking more and more components into it).

Currently, there are two hops from the GPU to the CPU:

Today: GPU --(PCIe)--> chipset --(FSB)--> CPU

According to the slides that wbmw linked to, the first Nehalem implememtation will replace the FSB with Quickpath:

Bloomfield: GPU --(PCIe)--> chipset --(Quickpath)--> CPU

Then with Lynnfield, one hop is being completely eliminated, so all that is left is a direct link between the CPU and GPU:

Lynnfield: GPU --(PCIe)--> CPU


The question you should be asking is this: How much will integrating this chipset functionality into the CPU (and thus removing one of these hops altogether) improve overall system performance?

I have no idea, but I'm anxious to find out...

Remember, Quickpath was meant for multiple-socket systems, and really shines in that space. We may see some computer makers offer initial single-socket Nehalem systems with one Quickpath link, but that will only be a stopgap until Intel can release Lynnfield (which eliminates the system bus altogether).

In two years, I expect to see two general system architectures from Intel that are fully optimized for their markets:

1) For mobile and desktop: Single-socket CPU/chipset with either a direct link to a GPU, or with a GPU also integrated into the CPU socket.

2) For servers/workstations: Multiple-socket CPUs with direct Quickpath links to all other CPUs and the chipset. Bandwidth galore.

That's how I see things playing out, anyway...