When we got down to some overclocking experiments, we discovered something not very nice: the mainboard was extremely unstable at any frequencies even slightly over 300MHz FSB. Of course, maybe the mainboard designed for financial professionals isn’t intended to deal with something like overclocking at all, and that was something I thought about at first. Despite this fact, I kept trying and finally discovered the source of the issue. When digging through the options of the mainboard BIOS I enabled the Hyper Path 3 parameter intended to accelerate work with memory. Once I set it to Auto or Disabled, all overclocking issues disappeared.
In fact, when it comes to work with the memory, i975X chipset is not that issue-free. And we have some practical evidence of that. We have already tested quite a few DDr2 memory modules in Core 2 Duo based platforms. In the beginning we ran the tests on ASUS P5W DH Deluxe (Intel 975X) and P5B Deluxe/WiFi-AP (Intel P965) mainboards, but then we had to give up the P5W DH Deluxe, because we couldn’t get stable operation at high frequencies. Now these data have been officially confirmed.
For instance, the user’s manual to ASUS P5W64 WS Professional mainboard lists the following limitations when working with the memory:
- Due to the chipset limitation the mainboard can only support up to 8GB of memory. You may install a maximum of 2GB DIMMs on each slot, but only DDR2-533.
- Some old-version DDR2-667 may not match Intel’s On-Die Termination (ODT) requirement and will automatically downgrade to run at DDR2-533.
- Due to chipset limitation, DDR2-667 with CL=4 will be downgraded to run at DDR2-533 by default setting. If you want to operate with lower latency, adjust the memory timing manually.
- Due to chipset limitation, DDR2-533 with CL=3 will be downgraded to run at DDR2-400 by default setting. If you want to operate with lower latency, adjust the memory timing manually.
Do not forget that during successful overclocking of Intel Core 2 Duo E6300 processor, ASUS P5B Deluxe mainboard allows the memory to run as 1:1: you can set it as DDR2-533, i.e. the memory will work at over 900MHz frequency. In case of ASUS P5W64 WS and P5W DH Deluxe mainboards, you should use a lowering 4:3 divider, so that the memory is set as DDR2-400. As a result it will run at 700MHz speed.
Speaking of CPU overclocking I would like to point out that the mainboard could run stably at 460MHz FSB speed. In this case processor Vcore was set to 1.4V and the Vchipset – to 1.8V.
With ASUS P5W DH Deluxe configured the same way, we could get only 10MHz better result. Maybe it was so because that mainboard allowed raising the chipset voltage to 1.85V against 1.8V by ASUS P5W64 WS., and we all know that successful overclocking depends a lot on the voltage on the chipset North Bridge. Needless to say that we managed to overclock the CPU to 493MHz FSB on ASUS P5B Deluxe mainboard.