Iâ€™ve already posted here
about how the newer BIOSs for the P5B Deluxe affect voltage when overclocking. But after measuring how significant the actual power consumption that can be saved is, I figured it is worth a separate thread to highlight this. Hereâ€™s the situation with regard the P5B Deluxe using BIOS revision 0614:
If you overclock in the BIOS and leave the VCore setting in the BIOS on auto, the VCore gets increased above stock and becomes fixed. This means that Speedstep will have no affect on VCore and neither will RMClock. You may well not realise this is happening as CPU-Z continues to show the VCore value as being variable; it changes with Speedstep or RMClock.
Fortunately there is a way to overcome this problem; overclock the FSB with
Clockgen 220.127.116.11 Beta.
This allows you to regain control over the VCore using Speedstep or RMClock.
Using Clockgen I overclocked an E6600 to 3GHz using a FSB of 333 and with RMClock I set the VCore to the following settings: Multiplier 6 = 1.05V, Multiplier 9 = 1.212V. This resulted in CPU-Z displaying voltages of 1.128V & 1.288V.
I then measured the power consumption at idle and when running two instances of Prime95. I did this for the two different methods of overclocking and these were the results.
BIOS O/C = 108/153W
Clockgen O/C = 85/134W
Thatâ€™s a saving of 23W at idle and 19W at full load.
I mention the Asus P5W DH Deluxe in the thread title as I have a strong suspicion that recent BIOS revisions have made it function in the way that the P5B Deluxe does.
Could someone that has this board please test to see if this is the case. If you donâ€™t have a power meter there are other ways to test for this functionality.
1. I found Clockgen to be stable although I didnâ€™t test it much above 400 MHz. It happily went down to 166 MHz and I didnâ€™t try setting it lower than that.
2. The clock generator that the P5B Deluxe uses is the Cypress CY28551; you configure Clockgen to use it. I donâ€™t know if the P5 (non deluxe) uses the same clock generator.
3. The system at the 2GHz/3GHz setting was tested as being Prime95 stable for 8 and 3 hours respectively.