Intel Core i5 750 & i7 870 Review - PAGE 4

Overclocking the new Lynnfield processors, in both i5 and i7 flavors, is not only similar, but actually identical to overclocking a Bloomfield like the Core i7 920. The processors have a base clock (BCLK), which the processor's core, uncore (integrated memory controller and cache) clocks and the memory derive their clock from. By default, it is set at 133 MHz.

Once processor limitations were put aside by lowering the multiplier, I set off to find the maximum BCLK the DP55KD could reach. While many of the X58 motherboard's could reach 200 MHz with relative ease, the sample Intel board  used in this review could only manage a measly 182 MHz. Past this speed, it showed obvious signs of instability, from corruption to blue screens and freezes. Fortunately, it only required 1.30V Uncore to get there. Then, I simply moved the processor's multiplier back to its default value and increased the voltage slightly above 1.3V.

Surprisingly, it proceeded to boot into Windows without any issues. However, it wasn't quite stable yet, but nothing some more voltage couldn't fix. Here are the final overclocked settings used in this review.

Core i5 750

• Baseclock : 180 MHz
• Clock multiplier : 20x
• Processor clock : 3600 MHz
• Memory clock : 1440 MHz
• Processor voltage : 1.3125V
• Uncore voltage : 1.29V

Core i7 870

• Baseclock : 182 MHz
• Clock multiplier : 22x
• Processor clock : 4004 MHz
• Memory clock : 1456 MHz
• Processor voltage : 1.3375V
• Uncore voltage : 1.30V

Power Consumption

Intel has definitely done its homework in order to keep power consumption down. Using out of the box settings, the quad-core Core i5 750 actually manages to draw less power than a similar system using a dual-core processor. Once the clock is forced to always remain at 2.66 GHz, the system draws an extra 30W under both idle and load conditions. It's pretty clear the power saving features are doing their job and when Turbo kicks in it should improve performance as well. Overclocking doesn't affect idle consumption, although it draws 46 more Watts under load.

The Core i7 870 tells a similar story, but this HyperThreading-enabled processor does require quite a bit more power than it's little brother. When it's idle with default settings it's saving 42W compared to when it's forced to always run at 2.93 GHz. The 9W difference under load isn't quite as drastic, but it's still better than nothing. Once overclocked, it draws 42 more Watts under load.