X-bit labs

Multi-Core Confrontation: Core 2 Quad Q6600 vs. Core 2 Duo E6850 (page 5)

Category: CPU

by Ilya Gavrichenkov

[ 08/31/2007 | 12:01 PM ]

The second processor participating in our tests today, Core 2 Quad Q6600, arrived in our lab just not so long ago. Although these processors have been selling in stores for over one and a half years already, they became especially interesting quite recently. The thing is that on July 22 Intel not only cut all the processor prices down in half, but they also transferred these particular processor models to a more progressive G0 core stepping.

According to the official data, quad-core processors based on new core stepping boast lower heat dissipation and can work at higher temperatures than their predecessors. Thus, the heat dissipation of the new Core 2 Quad Q6600 modification on G0 stepping dropped from 105W to 95W.

We ere impatiently waiting for the Core 2 Quad Q6600 on the new core stepping to arrive in our lab. There were many reasons to believe that it would be better overclockable than its predecessors and it seems like a perfect opponent to the dual-core Core 2 Duo on G0 stepping.

Luckily, we have finally got our hands on a processor like that.

As you can see from the screenshot, Core 2 Quad Q6600 works at the nominal 2.4GHz frequency achieved as 9 x 266MHz. The total capacity of its L2 cache is 8MB, however it is split in two parts, each shared between a pair of cores within each die of the quad-core processor. The processors nominal VID was set at 1.2625V.

Note that the CPU participating in our tests is a serial unit. Its S-Spec is SLACR. This particular marking helps to distinguish this processor visually from the predecessor on B3 core stepping with SL9UM S-Spec. As you know, S-Spec is marked on the boxes of boxed CPUs and on the processor heat-spreader.

So, looks like Core 2 Quad Q6600 should overclock at least as well as Core 2 Duo E6850 as it is based on absolutely identical semiconductor dies, although twice as many. However, it is exactly the double number of dies within the same package that makes it harder to overclock quad-core processors on Core micro-architecture. Even such high-performance air-coolers as Scythe Infinity with two fans have hard time coping with Core 2 Quad cooling during extreme overclocking. By the way, this is exactly the reason why it is so important to pick the right cooling solution for Core 2 Quad processors, so don’t underestimate this task.

We managed to overclock Core 2 Quad Q6600 to 3.6GHz by raising the FSB frequency to 400MHz and pushing the voltage to 1.4V.

In this case the CPU passed successfully the 12-hour stress-test in Prime95 and completed a standard set of benchmarks.

Note that the temperature of some processor cores in this case hit pretty high values.

The memory worked just fine at 1600MHz with 7-7-7-20 timings and its voltage was increased to 1.9V.

Further overclocking of our Core 2 Quad Q6600 processor was possible theoretically, but required additional Vcore increase. Unfortunately, in our test platform with air-cooling it resulted in uncontrolled increase in processor temperature and throttling kicked in.