Overclocking Experiments

You have every right to expect mainboards on Intel X48 chipset to be a little better at CPU overclocking than their predecessors. Since this chipset supports higher FSB speeds, up to 400MHz, in nominal mode. However, only practical experiments will show if this is true or not.

 To check out the overclocking potential of the new Gigabyte GA-X48T-DQ6 mainboard we put together a special testbed that included the board, of course, 2GB DDR3-1800 from Cell Shock (CS3222580), OCZ GeForce 8800GTX graphics card, Western Digital Raptor WD1500AHFD HDD and SilverStone SST-ST85ZF power supply unit. The CPU was cooled with Scythe Infinity cooler.

First of all, we decided to determine the maximum FSB frequency when the mainboard would run stably with a dual-core processor. We used a 45nm Core 2 Duo E8500 with 3.16GHz nominal speed (9.5 x 333MHz). The stability was checked with a standard one-hour run of OCCT Perestroika 2.0.0a application.

Practical experiments showed that our system can run stably with a dual-core CPU at 450MHz FSB without any special tricks on our end. If the CPU and the memory can work in this mode the mainboard will definitely support it. You won’t even have to increase the North Bridge voltage.

When the CPU clock frequency multiplier is lowered to 8x, we could hit a more important psychological maximum of 500MHz. However, in this case we had to push the FSB and North Bridge voltages 0.3V up to ensure stability of our test system.

The record-breaking FSB frequency with a dual-core processor overclocked on GA-X48T-DQ6 mainboard equaled 525MHz. It was achieved by raising the FSB voltage 0.35V higher and increasing the North Bridge voltage by 0.4V at the same time.

In this case the system remained absolutely stable. The CPU worked at 4.2GHz frequency with Vcore set at 1.4V. Memory ran with 1.9V voltage setting and 7-7-7-20 timings at 1680MHz.

I would like to say that if you use different dividers to set the DDR3 SDRAM frequency at a lower value, the workload on the chipset North Bridge will reduce dramatically. As a result, you will be able to achieve system stability without any significant NB voltage increase. In our case when the FSB:DRAM multiplier was set at 5:8, we had to resort to one more trick to ensure stability: we manually raised Static TREAD Value (Performance Level) to 12, which has some negative effect on the memory subsystem performance.

So, it is not quite correct to claim that mainboards based on the new Intel X48 chipset boast significantly higher FSB overclocking potential than those on Intel X38. However, we may be able to reveal certain improvements during quad-core processors overclocking. Let’s check it out now. For the next round of experiments we upgraded the above described testbed based on Gigabyte GA-X48T-DQ6 mainboard with a Core 2 Quad Q9300 processor from the Penryn family that works at the nominal speed of 2.5GHz (7.5 x 333MHz).

As we know, quad-core processors overclocking by raising the FSB frequency stumbles upon first problems much sooner than dual-core processors overclocking. That is why it is not surprising that we had to really fine tune the BIOS parameters to ensure that our GA-X48T-DQ6 will run stably at 450MHz FSB with Core 2 Quad Q9300 processor. To pass the stability tests we had to increase the FSB voltage to its maximum, i.e. by 0.35V, while the NB voltage was set 0.25V higher. Only with these settings Core 2 Quad Q9300 remained stable at 3.37GHz frequency.

Further overclocking was even harder to perform. To get our testbed to work at 460MHz FSB, the chipset North Bridge voltage had to be set 0.3V higher. And at 470MHz FSN the system stopped booting the OS with any settings.

As a result, the maximum overclocking for a quad-core Core 2 Quad Q9300 processor on Gigabyte GA-X48T-DQ6 mainboard was the modest 3.45GHz frequency.

So, looks like Intel X48 chipset used for Gigabyte GA-X48T-DQ6 mainboard failed to improve quad-core CPU overclocking. You can get pretty much the same results for quad-core CPUs on older mainboards using Intel X38 or even Intel P35 chipsets.