Since Intel Skulltrail platform is first of all targeted for advanced users, Intel had to make sure that it features the sufficient options for successful CPU overclocking. And it was not only about increasing the processor clock frequency multiplier. LGA771 Core 2 Extreme QX9775 processors, like all other Core 2 Extreme CPU models, boast an unlocked clock frequency multiplier. However, despite this fact, Intel D5400XS mainboard has quite advanced settings for successful CPU overclocking not only through multiplier increase but also by raising the FSB bus frequency.
Let’s check out overclocking friendly BIOS Setup parameters available on Skulltrail platform. All options dealing with system configuring are gathered together in the Performance section of Intel D5400XS BIOS.
Processor Overrides section contains the main parameters: CPU multiplier and FSB frequency. These values are set simultaneously for both processors, which prevents you from overclocking each CPU separately. However, the processor Vcore can be set independently for each CPU. The maximum available voltage setting is 1.6V, plus you can add another 0.3V through CPU Voltage Offset parameter. You can also increase the FSB voltage (up to 1.5V) and chipset North Bridge voltage (up to 1.6V).
Memory Overrides section provides access to memory latencies and voltage. You cannot adjust memory frequency here, it is being set automatically basing on what the SPD reports. Here you can also come across some typical server options such as disabling Snoop Filter and switching the memory controller operational modes.
Bus Overrides section allows adjusting PCI Express bus frequency.
Reference Voltage Override page offers to adjust base GTL and FSB voltages.
We couldn’t pass on the practical experiments revealing the potential of Core 2 Extreme QX9775 CPUs of the Skulltrail platform. Since these processors are based on 45nm cores they should overclock pretty well. For example, similar LGA775 quad-core Penryn processors can easily get past 4GHz frequency with a slight Vcore increase alone.
To ensure proper cooling of CPUs in our Skulltrail platform we use a couple of Zalman CNPS9500 coolers. We checked the platform stability with Prime95 25.5 utility.
As we have expected, Core 2 extreme QX9775 proved up to our expectations. Skulltrail system remained stable with CPU voltage at its nominal level and the multiplier at 9x, i.e. at 3.6GHz CPU speed.
To ensure that the system is stable with the next multiplier setting of 10x, we had to raise the CPU Vcore. The system remained fully stable only at 1.4875V set for both processors.
In this case we overclocked the processors by 25%, i.e. to 4GHz frequency.
We didn’t dare overclock any further because the system heated up severely at 4GHz already: our CPUs temperature read 90ºC.