Intel Core 2 Extreme QX6700 review

David Fearon Read more October 7, 2009

£540

Price when reviewed

If you thought dual-core processors were cutting edge, you’re already behind the times. Quad core is here, in the form of the Extreme QX6700.

The processor itself isn’t a “native” quad-core part. By this, we mean the four execution cores don’t exist on a single, integrated silicon die. Much like Intel’s original dual-core part, the Pentium D, the QX6700 is essentially two existing 2.66GHz Core 2 Duo E6700 parts in a single physical package, giving four cores overall. The specification for each of the two dies in the package remains the same as the dual-core components: each has 4MB of Level 2 cache shared between two cores, making for 8MB in total for the part.

There’s good news when it comes to compatibility: the QX6700 comes in a standard LGA 775 package, the same physical form factor as Core 2 and latter Pentium 4s. If your motherboard is based on the Intel 945, 965 or 975X chipset, it should be a drop-in replacement, but will probably require a BIOS upgrade. We flashed the latest BIOS into our test rig based on an Intel 975XBX motherboard, dropped in the quad-core part and it booted up without a murmur. Once Windows was up and running, bringing up Task Manager and checking out the Performance tab showed four CPU-load traces, which was very satisfying.

When it comes to the benchmark scores, the overall result – while very high – doesn’t tell the full story and highlights what’s likely to be a considerable lag in terms of software catching up with quad core. The overall result of 1.89 in our test setup is beaten only by the dual, dual-core Xeon-equipped Mac Pro and other complete QX6700-based machines in this issue. But running through the benchmarks while monitoring the load on each core showed that, even though we use the latest versions of apps, they don’t fully utilise all four cores. In fact, 3ds Max was the only app to fully saturate every core. Our multitasking test – designed in the pre-multicore era but with this generation of CPUs in mind – also managed to use all four cores almost constantly, courtesy of Windows XP’s effective thread scheduling. Consequently, those two tests achieved scores of over 2, but the overall results (and indeed the 2D Graphics score, of which 3ds Max is just one part) were dragged down by the apps unable to use all the computing power.

A second downside is that, despite Intel’s aim for its past few generations of processors being to increase performance while reducing power consumption, the reverse is true in the case of the QX6700. Take Intel’s own claims that performance has increased by up to 70%, while TDP (thermal design power) has doubled to 130W, do some pretty basic maths and you’ll see that performance per watt has decreased by 15% in the best case.

So the reason for releasing the first quad core as an Extreme edition, with no mainstream desktop parts as yet, is clear: few people who’ve been used to the new sound of silence with their cool-running Core 2 Duo systems are going to be won over by screaming fans. We’d qualify this by saying that our test system used the stock fan provided for a Core 2 Duo and we didn’t experience any problems with overheating, although the reported core temperature did reach 70C when all four cores were working hard. So if you’re prepared to put up with a hot-running system, you can get away with less than full-on cooling, but you’ll rarely get down to the quiet levels of a Core 2.

Intel is claiming the first mainstream quad-core parts will be available in January 2007, but these will again be dual Core 2 Duo-style parts, relying on lower clock speeds to consume less power than the QX6700. It isn’t until parts based on the new 45nm fabrication process appear – perhaps by late 2007 – that power consumption will be able to drop to current Core 2 levels.
With a street price of around £600 ex VAT, the QX6700 is unlikely to be a mainstream success. But it does have attractions. Being an Extreme edition, the QX6700 is clock-unlocked. Quite aside from overclocking, it also means you can reduce the clock frequency to give a CPU that’s faster than anything else in quad-core-aware apps but will consume less power. It’s an expensive way to get a quiet system, but the choice is there. We’re not going to knock the QX6700 too hard for consuming so much power either: it’s an Extreme edition part designed for those who want maximum computing power at any cost. And in that department – matched to suitable apps – it delivers massively.