Like the Core 2 Quad processors, Intel’s latest Core i7 chips have four cores, but there are some significant differences that improve their performance over those of the other Intel chips here.
The older Core 2 Quad processors can work on four separate threads at the same time, but thanks to the reintroduction of Hyper-Threading (previously used on the Pentium 4) the Core i7 chips can work on eight threads simultaneously. As with the Core 2 Quad processors, only programs written to take advantage of multithreading are likely to show significant performance increases.
The other Intel processors here use the frontside bus (FSB) to communicate with the Northbridge of the chipset. This contains the memory controller and provides secondary high-speed links to the rest of the computer’s components. Core i7 processors use QuickPath Interconnect (QPI) instead of the FSB, and the memory controller has been integrated with the processor. Other components communicate with the processor using the QPI. The main purpose of this change is to prevent the system bottlenecks caused when multiple processors try to access shared memory through a single memory controller. This is similar to AMD’s processors, which use HyperTransport and also have integrated memory controllers.
This new interconnect technology means that Core i7 processors need a motherboard with an LGA1366 processor socket, making them incompatible with the more common LGA775-equipped motherboards. The Core i7’s integrated memory controller supports only DDR3 memory, so you can’t buy cheaper DDR2 kits. Currently, the high price of these components makes building a Core i7 PC much pricier than building one using the cheaper LGA775 Intel processors.
Both the Core i7 920 and 940 processors use a Nehalem core, which is manufactured using a 45nm process. They have 256KB of L2 cache and a further 8,192KB of L3 cache shared between all four cores, which should help reduce the need to access the comparatively slow system memory. The QPI runs at 2,400MHz. They were easily the fastest processors in our round-up, but the cheapest Core i7 processor, the 920, is expensive at £236. The 940 costs more than twice as much – a staggering £507 – for only a small speed gain over the 920. Although the Core i7 processors are cheaper than some of the most expensive Core 2 Quad and Core 2 Extreme processors, it’s only worth building a Core i7 PC if you need the fastest possible performance and have the money to pay for it.