The ultimate guide to Intel's Core i7

Intel's new Core i7 processor is preposterous. There's no other way of putting it. It is simply the world's fastest PC processor and it pumps out performance numbers so spectacular it's enough to make you laugh out loud at the sheer, giddy ludicrousness of its existence.

In a way, that's not giving away a great deal. We always knew it would take the PC performance crown. After all, the existing Core 2 CPU was the previous title holder and Core i7 was bound to be a least a little quicker. But we still didn't expect the brutal, fratricidal hatchet job that is about to unfold.

Mostly, we weren't expecting it because Core 2 itself was so damn good. Before we got our hands on Core i7, it was hard to imagine how a new CPU could possibly humiliate its progenitor as comprehensively as the Core 2 managed with the ill-fated Pentium 4 processor. We also had an inkling the microarchitecture that underpins Core i7, codenamed Nehalem, is more about laying solid foundations for the future than delivering a knock out blow at launch.

Intel is planning to dramatically increase the core counts of its processors in coming years. So a modular architecture with bags of bandwidth will be essential to keep performance scaling efficiently. That's exactly what Nehalem delivers. With more threads, more bandwidth and more efficient load balancing, it has been designed from the ground up to be a mean, lean, parallel processing machine.

Thing is, at launch Core i7 only comes in quad-core trim. Hence, it's the upcoming eight-core version, pencilled in for a late 2009 debut, that we thought would be the defining model in the Core i7 family, the chip that really allows the work Intel has done with the Nehalem architecture to shine. It may still turn out that way. But the first Core i7 chips are a bloody good start.

Fundamental rethink

To pull that off, Intel has fundamentally rethought the way it builds PC processors. The big change involves the shift towards a much higher level of feature integration on the CPU die itself. Strictly speaking, it's not actually a new approach.

AMD's CPU architectures have been guided by essentially the same philosophy of integration and modularity since the Athlon 64 appeared in 2003 with an on-die memory controller and HyperTransport links. But as we shall see, the details of Intel's implementation and the performance it delivers are unlike anything seen before in the PC.

The first part of the Core i7's integration riff is the introduction of truly monolithic multi-core processor dies. No longer will Intel bodge up quad-core products by lashing together a pair of dual-core CPU dies in a single processor package, as it has done to create all of its existing Core 2 quads. Instead, all the execution cores in Core i7 processors are fused into a single die.

The key benefits here are improved bandwidth and reduced latency. The multi-die approach used for Core 2 was a reasonable short term solution, but technically, it's a bit of a kludge. It forces communication between the two processor dies to be routed off the CPU package to the northbridge chip on the motherboard and back again via the front side bus. Not exactly ideal.