All performance tests were run on the following test platform:
- Asus P6X58D-E rev. 1.00G mainboard (LGA1366, Intel X58 Express, BIOS version 0303);
- Intel Core i7-930 CPU (2.8 GHz, Bloomfield D0);
- 3 x 2048 MB Kingston KHX12800D3LLK3/6GX, (1600 MHz, 8-8-8-24 timings, 1.65 V voltage);
- HIS HD 5850, H585F1GDG graphics card (ATI Radeon HD 5850, Cypress, 40 nm, 725/4000 MHz, 256-bit GDDR5 1024 MB);
- Seagate Barracuda XT HDD: ST32000641AS (2 TB, SATA 6 Gbps, 7200 RPM, 64 MB cache);
- DVD±RW Sony NEC Optiarc AD-7173A optical drive;
- Scythe Mugen 2 Revision B (SCMG-2100) CPU cooler;
- Zalman CSL 850 thermal interface;
- OCZ GameXStream OCZGXS700 (700 W) PSU with Zalman ZM-F3 fan;
- Open testbed.
We used Microsoft Windows 7 Ultimate 64 bit (Microsoft Windows, Version 6.1, Build 7600) operating system, Intel Chipset Software Installation Utility version 188.8.131.525, ATI Catalyst 10.7 graphics card driver.
Operational and Overclocking Specifics
If you do not know how to overclock LGA1366 processors and what problems there can be with that, you can refer to the following reviews:
- First Look at Intel Nehalem Microarchitecture
- New Hit from Remake King: Intel Core i7 Review
- Intel Core i7-920 Overclocking Guide
We didn’t have much trouble refreshing our knowledge of how to overclock an LGA1366 platform, but we first want to say a few words about the processor we used. It was an Intel Core i7-930. As a general rule, junior CPU models in a series are considered the most optimal choice for overclocking. The junior Core i7 model is Intel Core i7-920 but it exists in two versions: with the old C0 and with the new D0 stepping. The Intel Core i7-930 is available with the new stepping only, so there can’t be any confusion, which is the reason why we preferred it for our tests. The CPU lowers its frequency and voltage when idle.
When under load and with the Intel Turbo Boost technology turned on, the CPU lifts its clock rate up to 2.93 GHz. On many mainboards, including the P6X58D-E, Turbo Boost is set up in such a way that the CPU frequency multiplier doesn’t ever drop to its default value. In other words, we can use the Turbo Boost option to simply increase the multiplier by x1.
If the CPU load is low (when only one of the four CPU cores is in use while its power consumption and temperature remain within reasonable limits), the Intel Turbo Boost technology increases the CPU frequency multiplier by x2 rather than by x1. The Everest utility doesn’t notice that but you can use the TMonitor tool instead.
We can remind you that Intel Turbo Boost will only work fully if you enable the Intel C-State Tech option in the mainboard’s BIOS and leave the C State package limit setting at its default (or explicitly set it at C6). Otherwise, the voltage will be lowered less in idle mode while the CPU frequency multiplier will only be increased by x1 irrespective of load.
However, Intel Turbo Boost is only appropriate for the mainboard’s default operation mode. If you overclock it, the increased multiplier may make your system unstable. The simplest, but not the best, option is to disable that technology in the BIOS. On the other hand, Turbo Boost increases the CPU frequency multiplier, so you can overclock to a lower (i.e. more stable) base clock rate. Besides, it increases the CPU voltage dynamically under load. Coupled with the technology that counteracts a CPU voltage drop under load, it means we can increase the CPU voltage less without compromising stability. For Turbo Boost to increase the CPU multiplier by x1 only, we can set the C State package limit setting at C1.
Overclocking through increasing the base clock rate raises the rest of related frequencies besides the CPU one, but mainboards generally work well at increased frequencies of the CPU-integrated North Bridge and QPI bus. You will only have to correct the memory frequency and timings as necessary.
For example, to overclock our processor to 3.9 GHz we didn’t have to increase any voltages at all. We just relied on the automatic voltage increase (thanks to Turbo Boost) and on the technology that counteracted a CPU voltage drop under load.
All of the CPU’s power-saving technologies work in idle mode, lowering both the multiplier and voltage.
Intel doesn’t have a 3.9GHz Core i7 processor and we don't know if they will ever offer one. So, our overclocking experiment is quite successful. We were only let down by our Kingston KHX12800D3LLK3/6GX memory. From our roundup called Triple-Channel DDR3-1600 Kits for LGA1366 Systems, we knew that it couldn’t overclock much above its rated frequency of 1600 MHz. Now we also made sure that memory kit did not allow lowering the timings much at low frequencies. We wanted to set 6-6-6-18 but had to be content with 7-7-7-20. The memory voltage could be left at 1.5 volts, yet we were somewhat disappointed anyway.