Intel Core 2 Extreme: 1333MHz PSB and Beyond


Core 2 Extreme Overclocking

Putting 'Extreme' back into the Extreme

In our Intel Core 2 (Conroe) Performance Review article, we briefly mentioned about the initial rumors of the Core 2 Extreme clocks. There was talk about it debuting at 3.33GHz on a 1333MHz PSB, but of course that didn't happen. While we're in no position to pout about the Core 2 Extreme X6800, especially after seeing its performance, we couldn't get rid of that nagging feeling that the X6800 just wasn't extreme enough since it was just a multiplier increment over the regular Core 2 Duo E6700.

We wanted to satisfy our curiosity as to how the Core 2 Extreme would perform if it did meet the speculated specifications on release. Our overclocking platform of choice - Gigabyte's GA-965P-DQ6. At the present moment, we find that many initial Core 2 motherboards' BIOS do not properly detect Core 2 processor capabilities, sometimes restricting multiplier selection and others lack the necessary voltage and tweaking selections. The GA-965P-DQ6 happens to be one of the better boards to support the unlocked X6800 and possess great voltage granularity, a perfect combination for our overclocking efforts.

To do this, we overclocked the Core 2 Extreme X6800 to the ideal 3.33GHz with a 1333MHz PSB using a 333x10 FSB to CPU multiplier ratio and then topped it off with DDR2-1066 memory. However, we didn't just stop there.

Remember, this is not an actual product nor has Intel hinted as yet that there will be desktop 1333MHz PSB processors anytime soon or official support for DDR2-1000, but that doesn't stop us from living the dream now does it?


Maximum Overclocking

Next, we did some real overclocking to see just how scalable the Core microarchitecture can be. Intel's Netburst has produced scalable processors with good overclockability, but are bogged down by high power consumption and operating temperatures. The Core 2 is almost a total opposite, starting at modest sub-2GHz speeds. The Core microarchitecture's short pipelines would have reduced the processors scalability in terms of frequency, but its ultra efficient power consumption and low thermals should give it plenty of room.

In our overclocking tests, we took the same Core 2 Extreme X6800 and went all out to see just how far we could push the processor on stock Intel air-cooling. That's right, we didn't use fancy third-party coolers for this nor did we rely on exotic cooling techniques. The standard Intel boxed processor cooler was used to realistically set a stage for overclocking bandwidth right out of the box.

Our result? A final clock of 3.60GHz at 360x10. Not exactly the best overclock on the Conroe core, but it nearly puts the Core 2 Extreme at the same speed of the Intel's Pentium Extreme Edition 965, which runs at 3.73GHz. In the end though, our overclocking effort was possibly limited by the older B1 stepping of our X6800. The newer B2 stepping on the retail processors seems to have better overclocking performance from what we've been able to gather. On the other hand, the GA-965P-DQ6 showed a great overclocking bandwidth, with the retail boards clocking up to 480MHz with ease. However, since we were testing the processor and not the motherboard, the 360x10 setting was more ideal than say 450x8 after taking into consideration memory limitations and keeping chipset voltage on the low.