All performance tests were run on the following test platform:
- Intel DX58SO2 mainboard (LGA1366, Intel X58 Express, BIOS version 0765);
- 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);
- Kingston SSD Now V+ Series (SNVP325-S2, 128 GB);
- Scythe Mugen 2 Revision B (SCMG-2100) CPU cooler;
- ARCTIC MX-2 thermal interface;
- Cooler Master RealPower M850 PSU (RS-850-ESBA);
- Open testbed built using Antec Skeleton system case.
We used Microsoft Windows 7 Ultimate SP1 64 bit (Microsoft Windows, Version 6.1, Build 7601: Service Pack 1) operating system, Intel Chipset Software Installation Utility version 22.214.171.1245, ATI Catalyst 11.2 graphics card driver.
Operational and Overclocking Specifics
We had no problems assembling our test configuration on this mainboard but our first attempt to start everything up almost failed. The CPU fan would not spin up and at first we attributed this to an aggressive speed management algorithm. The rest of the fans connected to the mainboard are slowed down by default but you can let them stop completely. Unfortunately, our mainboard just turned out to have a defective CPU fan connector.
Anyway, we proceeded with our tests. Our Intel Core i7-930 processor can overclock from its default 2.8 GHz to 3.9 GHz and we repeated this overclocking on our Intel DX58SO2 mainboard. To achieve that CPU frequency we increased the base clock rate to 177 MHz and added 0.025 volts to the default CPU voltage.
The mainboard has a technology for counteracting the CPU voltage drop under load. Besides turning it on and off, you can also set it to a medium mode. However, we didn't notice any serious difference between the medium and the turned-off states of that technology whereas the biggest voltage drop was observed when the technology was set to its maximum mode. Therefore we used the medium mode and the CPU voltage would increase from the default 1.2 to 1.3 volts under load (although we only had to increase the CPU voltage to 1.28 volts to ensure stability with other mainboards, which we used with our CPU previously). The power-saving technologies were all active during our tests, lowering the CPU frequency multiplier and voltage in idle mode.
However, the memory frequency isn't very high, just slightly over 1400 MHz, with such overclocking. This is not the mainboard issue but the peculiarity of our Kingston KHX12800D3LLK3/6GX memory modules. In our earlier tests we found out that they have very low overclocking potential. They cannot work at clock rates much higher than their default 1600 MHz and do not support low latencies at low frequencies, either. So, we have to set the CAS Latency parameter at 7. Therefore, we decided to give up Intel Turbo Boost technology which increases the CPU multiplier by x1 in order to overclock the CPU to 3.9 GHz at a higher base clock rate. This would also increase the rest of the related frequencies, including the memory frequency. We achieved the desired CPU frequency at a base clock rate of 186 MHz and not just 177 MHz.
We hadn't used this mode in our previous tests, fearing that the power consumption would grow too much due to the higher CPU voltage. With Intel Turbo Boost enabled, we only added 0.025 volts to the default voltage of 1.2 volts, so the peak voltage was 1.3 volts. To achieve the same with Turbo Boost turned off, we had to increase the voltage by 0.0875 volts. The CPU voltage and the total power consumption of the system were the same under load, but the second setup led to a higher voltage in idle mode.
However, the power consumption in idle mode was actually lower with the second setup, i.e. with Intel Turbo Boost turned off. Why? The answer lies with C-States parameter. When Turbo Boost was enabled, we had to prohibit our CPU to switch into deep power-saving modes so that Turbo Boost could increase its multiplier by x1 only, i.e. to x22 in our case. And when Turbo Boost was turned off, the CPU would disable unused subunits in idle mode, consuming less energy. Thus, overclocking with disabled Turbo Boost seems preferable because the power consumption of the system is lower in idle mode. And under load the performance is somewhat higher due to the increased frequencies of the various buses.