Intel Core i7 review

Intel's latest, fastest and most feature-rich generation of desktop CPUs, formerly codenamed Nehalem and now branded Core i7, is here. After more than a year of anticipation we finally have hardware to test, but can it live up to the hype?

At first glance, the three new chips that make up the initial Core i7 family look disappointingly ordinary. They're all quad-core 45nm parts, running at speeds from 2.66GHz up to 3.2GHz. On paper, nothing seems to set them apart from the existing Core 2 Extremes.

But as soon as you clap eyes on one it's apparent that Core i7 represents a break with the past: the new CPUs are larger than their forebears in the Core family, and to accommodate them Intel has introduced its first new desktop socket in four years. LGA 1336 (known as Socket B) uses the same ZIF design as the familiar LGA 775 architecture, but it incorporates many more contacts.

One reason for this expansion is that with Core i7 the CPU takes over memory controller functions that were previously handled by the north bridge. In place of the old front side bus it now has a dedicated high-speed connection directly to the system RAM, just like the HyperTransport used by AMD processors. Intel calls its new bus the QuickPath Interconnect (QPI).

It's worth noting that Core i7 is Intel's first DDR3-only platform. It uses a three-channel memory controller, so you can expect to see DDR3 DIMMs appearing in three-packs soon. You don't have to install modules in threes, but if you do you can expect a small performance benefit, as with existing dual-channel controllers.

These big architectural changes are backed up by some less visible advances. Until now, Intel's quad-core processors have been constructed from two dual-core dies, but now Core i7 brings together four cores on a single die. It's also Intel's first processor design to use an L3 cache, shared between all four cores.

Once again, Core i7 resembles AMD's Phenom more than its Intel predecessors. As usual, however, Intel has been far more generous with cache RAM than its rival, equipping the i7 with 8MB of L3 cache while AMD's quad-core parts get just 2MB.

The icing on the i7 cake is a pair of logic features found on neither the Phenom nor the Core 2. The first is Intel's HyperThreading (HT) technology.

This allows each CPU core to present its spare execution capacity to the OS as a second core, which can speed things up whenever more than four process threads need to be serviced simultaneously. As most applications are single-threaded, it's unlikely to make a big difference in everyday use; but it's fun to see eight CPU graphs appear in the Windows Task Manager.

The second is a new feature called Dynamic Speed Technology, which allows the processor to detect when load is unevenly balanced and automatically boost the speed of the cores with the most work to do. Idle cores are clocked down to keep power consumption within tolerance. Don't expect to see dramatic overclocking: from early technical documentation, it looks like the biggest dynamic clock rise you'll see is 266MHz.

The fastest PC in the world

With all these new technologies, we were hopeful that the Core i7's performance would belie its seemingly unremarkable specifications, and we weren't disappointed. A system built around the low-end Core i7-920, running at 2.66GHz, tore through our benchmarks with a final score of 1.86. That's distinctly faster than a comparable system running the top-end Core 2 Extreme QX9770 (see the table above for comparisons with other processors).