We carried out our tests on a testbed that included the following components:
- Intel DX79SI mainboard (BIOS version 0380);
- Intel Core i7-3960X Extreme Edition CPU (3.3-3.9 GHz, Sandy Bridge-E rev.C0, 32nm, 130 W, LGA 2011);
- 4 x 4 GB DDR3 SDRAM Corsair Vengeance CMZ16GX3M4X1866C9R (16 GB, 1866 MHz, 9-10-9-27 timings, 1.5 V voltage);
- MSI N570GTX-M2D12D5/OC graphics card (Nvidia GeForce GTX 570, GF110, 40 nm, 786/4200 MHz, 320-bit GDDR5 1280 MB);
- Crucial m4 SSD (CT256M4SSD2, 256 GB, SATA 6 Gbps);
- Zalman CNPS12X CPU cooler;
- ARCTIC MX-2 thermal interface;
- CoolerMaster 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 220.127.116.112, Nvidia GeForce Driver 285.62 graphics card driver.
Operational and Overclocking Specifics
We didn’t have any [problems during the testbed assembly on Intel DX79SI mainboard, the system fired up just fine, too. The mainboard worked impeccably in nominal mode: all power-saving technologies and Intel Turbo Boost technology worked correctly and changed the processor clock frequency multiplier and core voltage depending on the current operational load, the memory timings and frequency were also set to correct values. The onboard PC-speaker, which couldn’t be turned off, was a little annoying, as well as the use of F2 key for entering the BIOS. In fact, this is a standard peculiarity of all Intel mainboards, but before they also allowed using the “Del” key for that purpose. Unfortunately, Intel DX79SI mainboard doesn’t support this feature any more for some reason, so when you forget about it and go for the Del key you miss the window for accessing the BIOS and need to reboot again.
We were a little disappointed that the mainboard was unable to adjust the rotation speed of a three-pin processor fan. I have to remind you that the majority of contemporary mainboards for some reason lost this useful feature a while ago. We mentioned multiple times in our reviews that only Gigabyte mainboards were currently capable of doing so, but now that they have completed the migration to UEFI BIOS, this is no longer the case. In the comments to one of our latest articles one of our readers insisted that Intel mainboards could do it perfectly fine, so we hoped it would be the case. However, our hopes didn’t come true. Even extended fan configuring functionality didn’t help. You can connect the CPU fan to a different connector, you can assign a fan a “processor fan” status in the BIOS. All three fan connectors, except for the standard CPU fan connector, will lower the rotation speed of a three-pin CPU fan. However, they can’t adjust the rotation speed depending on the temperature and the fan won’t speed up even if the CPU utilization and temperature will go up.
However, all these are little things and the more serious problems surfaced only during processor overclocking, because we uncovered a very strange dependency between the processor Vcore and memory frequency. To guarantee that our processor will work stably when overclocked to 4.4 GHz, we had to add at least 320 mV to its default core voltage. However, it turned out that in this case we couldn’t increase the memory frequency: when we raised it to 1866 MHz or even 1600 MHz the OS refused to boot. Once we lowered the desired core voltage increase to 300 mV or less, everything loaded fine, but the system failed to pass the tests – it would only pass the tests at the nominal 1333 MHz memory frequency setting. As a result, we had to stop at 4.3 GHz CPU frequency accompanied by a corresponding increase in the memory clock.
We always overclock mainboards in such a way that they could be used for a prolonged period of time in this mode. We do not try to make our life easier by disabling any of the mainboard features, such as onboard controllers, for example. We also try to keep the CPU's power-saving technologies up and running normally to the best of our ability. And this time all power-saving technologies remained up and running even in overclocked mode lowering the CPU voltage and frequency multiplier in idle mode.
I have to say that our CPU sample wasn’t the best one in terms of overclockability and it could only go as high as 4.4 GHz. This is an engineering sample with C0 processor stepping, while the mass production units have C1 processor stepping, and we even came across a few ones with C2 processor stepping in retail channels. We will most likely replace this CPU with another unit, but we didn’t believe that there will be a mainboard out there unable to overclock our CPU to this relatively low frequency of 4.4 GHz. Therefore, we were even questioning whether we chose the overclocking mode correctly. Maybe we should have sacrificed higher memory clocks to ensure that the CPU overclocks better. However, all our doubts vanished after a series of performance tests.