Intel’s Core 2™ Extreme QX6700: Quad Core Performance Preview

by John Reynolds




Announced by Intel in September, the Core 2 Extreme QX6700 quad-core processor was originally slated for debut in 1Q, 2007. Yet the company has decided to aggressively follow their Core 2 Duo launch by moving up the release of their first quad-core CPU to this fall. Rumblings of an imminent announcement from AMD on their 4×4 platform may have played a role in Intel’s decision, with the company seeking to garner whatever mindshare and perceived market leadership that may be associated with being the first to offer a desktop quad-core platform. This multiplicity of execution cores is undeniably an exciting period in the history of the desktop CPU’s evolution, at least from a hardware enthusiast’s perspective; from the software point of view, particularly that of PC gaming, however, SimHQ is concerned that developers may struggle for several years before releasing titles capable of taking advantage of these additional cores. With the advent of next-generation consoles and their multi-core CPUs, game developers are undoubtedly being spurred to code their titles for optimized SMP operations, yet the nature of creating and releasing a major title at this point requires millions of dollars and years of development. Many games released even in the second half of this year often show little advantage running on dual-core parts. SimHQ’s examination of the QX6700 will therefore seek to show our readers whether or not they can benefit from Intel’s quad-core processor in their home PCs.

Intel’s Core 2 Extreme QX6700 — code-named Kentsfield — is essentially constructed of two separate Core 2 dies on a single-socket package, both clocked at 2.66 GHz; SimHQ, however, will leave it to home users and hardware enthusiasts to debate amongst themselves whether or not the processor is truly a quad-core CPU (and, hopefully, also fairly apply whatever standard or logic that’s used toward AMD’s upcoming 4×4 platform). Each processor has 4MB of L2 cache shared by the two cores on each die, giving the QX6700 a total of 8MB of L2 cache. Intel’s 65nm fabrication process was used, giving the QX6700 a 130 watt TDP rating. This figure is essentially double that of a single E6700’s 65w TDP rating (75w for the 2.93 GHz X6800), though Intel is quick to point out that with their smart power management it’s doubtful that all four cores will be running at full clock speed all of the time. With portions of this quad-core design going unused at times, one of the cores, or even one of the two dies, could be idle, thereby letting the part operate well below its maximum rating. Intel included their RCFH4 fan with the QX6700 review kit, which is essentially identical to previous Socket T stock coolers included with retail PIB purchases.

The QX6700 also includes the same technology as the Core 2 Duo processors, such as Advanced Smart Cache (dynamic sharing of L2 cache between cores on a die), Wide Dynamic Execution (higher instruction efficiency and the ability to issue four instructions per clock cycle as opposed to only three in earlier architectures), Intel 64 (support for 64-bit platforms), Intel VT, and Execute Disable Bit (stopping malicious code from running in memory space marked as executable). As such, Intel’s marketing suggests that the QX6700 would work well in either a high-end desktop machine or in a business server environment.

As noted above, the Core 2 Extreme QX6700 is basically two Core 2 E6700s (2.66 GHz) sandwiched together into a single CPU package. The two dies do not directly communicate with each other, and as such are required to share the 1066 MHz front-side bus of the 975X chipset and its bandwidth. Intel claims that this provides both Core 2 dies with sufficient bandwidth even when all four execution cores are in heavy use, and the new 975XBX2 motherboard included in the review kit has been updated to include DDR2/800 support. Earlier versions of the board, including the 975XBX (Bad Axe) that shipped with the initial Core 2 Duo review kits, were limited to DDR2/667 memory, and it’s possible that owners of some 975XBX boards may have to upgrade for quad-core support. 975X chipset motherboards labeled as “quad core ready” should work fine with the QX6700, but current owners should carefully check on their particular board before buying once the new processor become available.

The Intel D975XBX Motherboard

As an Intel part with the words Extreme Edition in its title, the price for the QX6700 is the standard $999 in units of 1,000. This is the same price as the Core 2 Extreme X6800 since Intel expects the two processors to coexist on the market for some time to come. The E6700 (2.66GHz), the fastest non-Extreme Core 2 Duo, currently sells for slightly over $500.

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