Flash to most current bios - when i did mine it was 0405 but there is at least 1 newer one.
I pulled the sb and nb off to replace the tim and improve cooling, and also pull the pretty (stupid) shrouds of both of them to get some airflow on them.
Even if you don't replace the tim with as5 etc, i would carefully pry the gold covers off the SB and NB -they are on with adhesive and easiest to remove without damaging them if you pull the nb and sb off the mobo. Then save them in case you need to rma the mobo. Here is a pictorial guide
http://www.xtremesystems.org/forums/showthread.php?t=106563
I disabled every hardware feature in bios that i don't use.
On mine with a 6400 i maxed all the V settings except cpu - my mem likes v at 2.45, yours may not like as much but i would set it to at least 2.1v.
I left cpu V at auto but soon bumped it at 300 fsb to 1.3V.
It is always good to know how far your chip will go on the minimum VC.
lock pci at 33
i have been leaving pci-e at auto on my asus mobo's, but the ds3 needs to have it set to 100 - haven't experimented with it that i recall or noted to see if it affects max oc on the p5b-d.
leave your mem at auto/spd till you start maxing your cpu - my std oc'ing practice; although with known great mem i will often run slightly tighter timings.
I expect you will want to keep your mem at 1:1 - you can check everything is set right with cpuz.
I am pretty sure I disabled hyperpath in the chipset section ... i didn't note it down since i automatically do it on all my asus mobos since i oc them all. It doensn;t work once you get to a decent oc and will limit your oc.
Then just keep raising fsb until no post/boot. I had to start bumpung my VC at 300 fsb, and again at 400 fsb. I wasn't taking my time so i was bumping fsb a lot until i got to 400.
Make sure you have asus probe on to monitor temps as you add fsb and VC.
I still have not gone back to lower all the sb, nb & ich V's to see how much i really needed to bump them if any. I like to max them until i get my max cpu oc, then trying lowering them one at a time until you start getting unstable.
Although some of these V settings on the DS3 for example, seem to reduce the OC!
When i try the latest bios (i am currently on 0405), i will play with them some to see if i can improve my current 430 fsb stable folding oc.
Last steps after getting the max cpu oc is to see how mcu you can tune your memory. May involve playing with mch v too.
Have fun
