We tested the mainboards ability to overclock CPUs on an open testbed with the following configuration:
- Asus P5K mainboard (Intel P35 Express), rev 1.02G, BIOS 0414;
- Intel Core 2 Duo E6300 CPU (1.86GHz, FSB 266MHz, Conroe-2M, rev. B2);
- 2x1024MB Corsair Dominator TWIN2X2048-9136C5D;
- NVIDIA GeForce 8800 GTS 320MB graphics card;
- Seagate Barracuda 7200.10 HDD, ST3320620AS, 7200rpm, 16MB, SATA 320GB;
- Zalman CNPS9700 LED CPU cooler;
- OCZ GameXStream GXS700 PSU (700W).
Intel Core 2 Duo E6300 processor we used in our test session could work stably at 490MHz FSB if the voltage was increased to 1.45V in the BIOS. This has been proven on numerous mainboards in our previous test sessions. It would start with these settings on Asus P5K as well, but wouldn’t finish any tests, such as TAT, OCCT or Prime95.
At first we didn’t change the FSB Termination Voltage or North Bridge Voltage, however even their increase didn’t improve the system stability during overclocking. Although I noticed that if the Vcore was set to 1.45V in the BIOS the mainboard would lower it too much: down to 1.37V. Asus Commando, for instance, also lowers the voltage setting, to about 1.408V. We checked out different settings and experimentally found that 1.408V Vcore can be achieved if we set it to 1.487V in the BIOS. After that the overclocked system passed all tests successfully almost all the time.
Now I would like to share some of the observations I made during this test session: the mainboard seemed to be working fine, but them some errors would pop up and I couldn’t find a reasonable explanation for them.
So, the mainboard was working fine when the FSB Termination Voltage or North Bridge Voltage weren’t increased at all, and then it would refuse to boot when we raised them to 1.4-1.55V. The board would pass the tests and then would fail them; it would either reboot alright or freeze on restart. Sometimes, when we changed the BIOS settings just a little bit, such as increased the voltage slightly, the board wouldn’t start, but after we shut it down and powered it up again – it would work perfectly fine with the adjusted settings.
In fact, everything is not as scary as it may seem at first sight. If it had been happening all the time, then we could state that the board couldn’t overclock our CPU to its maximum. But the thing is that we encountered quite a few issues, but they never repeated. The errors occurred not too often, in a spontaneous manner and alternated all the time, but overall the board worked fine.
However, I have to admit that these coming and going errors do not allow me to claim the mainboard was stable, and no overclocking is possible without operational stability. All problems vanished once and for all when we set the FSB frequency only 5MHz lower. And we didn’t have to raise the FSB Termination Voltage or North Bridge Voltage: nominal 2.1V were enough for Corsair Dominator TWIN2X2048-9136C5D. And the CPU required only a slight increase to 1.475V Vcore. According to the monitoring tool, the processor voltage setting in the BIOS varied between 1.392V and 1.4V.
So, Asus P5K mainboard couldn’t overclock our test CPU to its maximum. It is drawback, but not a very serious one, I believe. 3.395GHz instead of 3.43GHz leaves us with 35MHz difference, which is too small of a difference to notice in performance benchmarks. 485MHz FSB is a pretty strong result, there are quite a few mainboards out there that cannot hit this frequency at all. Besides, we can’t say that Asus P5K mainboard cannot work at this frequency: it can, but it is not quite stable. We all know what wonders new BIOS updates may sometimes work, so Asus engineers really need to make a tiny little step to fix the issue. Although we definitely cannot say that falling 5MHz behind is an advantage.
As for Corsair Dominator TWIN2X2048-9136C5D memory, when we overclocked the system to 485MHz it worked in synchronous mode at 970MHz frequency with the default timings of 5-5-5-18 set by the board. It is not bad, but it is lower than its actual nominal, and every attempt to lower the timings to 4-4-4-12 failed, even if we tried to push the memory voltage to 2.2V. The system loaded Windows, but Prime95 utility reported an error very soon after that. We could also raise the memory frequency to 1164MHz with a higher divider. And even at its nominal frequency of 1142MHz and nominal voltage of 2.1V this memory refused to work on Asus P5K mainboard. We couldn’t get it to work neither at 476MHz FSB overclocking (in this case the memory frequency was 1142MHz), nor at 286MHz FSB (in this case its frequency was 1144MHz). The operating system loaded every time, but we just couldn’t pass any tests. So what does ASUS Super Memspeed Technology do and why doesn’t it work with Corsair Dominator TWIN2X2048-9136C5D? by the way, this memory is actually certified for Asus P5K as DDR2 1066.