Overclocking Results

Let’s get to the actual CPU overclocking experiments on Asus P6T mainboard following the plan mentioned in the previous chapter. At first, I couldn’t find the maximum base frequency, at which the board would remain stable. I lowered the processor clock frequency multiplier to the minimal value of x12, reduced the memory frequency, but the board would only boot. It couldn’t even load the OS, not to mention passing any of the stability tests. Luckily, I recalled that we have already talked about overclocking the same Intel Core i7-920 CPU on a board from the same family – Asus P6T Deluxe (see our article called Intel Core i7-920 Overclocking Guide for details). As we said before, when we lower the memory frequency on Gigabyte mainboards, they allow overclocking processors without increasing any of the voltages at all. Asus, however, needs “QPI/DRAM Core Voltage” parameter to be increased once you pass 175MHz base frequency limit. True, once we increased this voltage to 1.35V we could not only load the operating system but also pass all stability tests at up to 210MHz base frequency.

This is a good result, pretty typical for Intel X58 Express based mainboards. This is more than enough for our CPU to hit its maximum frequency, so the mainboard shouldn’t become a bottleneck. However, it did.

It doesn’t make sense to overclock processors on Asus P6T without increasing the voltages. We will be able to overclock it only to 152MHz base frequency and then we will lose all the advantages of this smart overclocking because Intel processor power-saving technologies will simply stop working. It also makes no sense to stop at 3.2GHz, because our CPU can do way better than that. However, when we increased the CPU Vcore, we had to deal with growing heat dissipation. As you remember, we had to also increase “QPI/DRAM Core Voltage”, that is why the temperature went up a lot. As a result, the best we could do was 190MHz base frequency that will give us 3.8GHz resulting clock speed with x20 frequency multiplier.

That is not too much, but we can enable Turbo Boost technology and limit the frequency multiplier increase to x21 maximum by setting “Intel C-STATE Tech” Parameter to C1. We had to set this limitation, because with x22 multiplier the CPU frequency got way too high and caused instability. This maneuver will allow us to slightly lower the base frequency and keep the resulting CPU speed at the same level or maybe even a little higher. However, our hopes didn’t realize. If we increase the voltage the CPU temperature goes up and at 94°C the board lowers the processor clock frequency multiplier from 21 back to 20. If we increase the Vcore a little less, the system fails the stability test. Therefore, we had to stop at 181MHz base frequency. Although we had to increase “QPI/DRAM Core Voltage” to 1.45V to ensure that our memory would work at high frequency with relatively low timings and to increase the CPU Vcore to 1.2375V, too. In this case the CPU temperature reached only 88°C during the “Small FFT” test in Prime95 program. It is also a high temperature, but we can deal with it.

What else could we do to lower the heat dissipation? For example, we could disable SMT technology that allows each core to process two computational threads at the same time. It will improve the performance in some cases, when the resulting CPU frequency is more important than the number of active cores and threads. However, higher frequency requires higher core voltage setting – up to 1.3V. The temperature kept growing, so this time we had to stop at 191MHz base frequency having reached 4GHz CPU speed. This time we managed to slightly increase the memory frequency and lower the timings at the same “QPI/DRAM Core Voltage” setting of 1.35V without losing stability.

Summing up everything I have just said about our experiments, let me offer you a comparative table of our Intel Core i7-920 CPU overclocking achievements on Asus and Gigabyte mainboards:

Asus P6T mainboard yields to Gigabyte during CPU overclocking, however, it is not too far behind the leader. Of course, we will have to disregard the most optimal overclocking mode when all Intel processor power-saving technologies keep working. In this mode, Asus definitely cannot compete.