i'm no expert but i just lowered each timing one by one untill my comp wouldn't boot then reset bios and set em to last known bootable settings I also tried lowering the voltage slightly but that caused strange things to happen...
just taking my trancend jetram from 5-6-6-18 to 4-5-5-12 bumped my vista cpu rating up by 0.2. Then I increased the HT to 1000 to give me another 0.1 cpu vista rating. now my 5600+ gets a 5.5 vista rating without overclocking it .
Very simple but time consuming to do.
All you need is your handy copy of memtest, a notepad and an empty evening.
Put the RAM Voltage to it's maximum specified and the timings at it's specified.
Starting at the top of the list, drop the timings one setting at a time.
Also, only one field at a time!
After each change, run a pass of memtest for at least 10 or 15 min.
If there are no errors, drop the same setting one more notch and retest.
Make sure an keep track of stable/not stable as it is just as likely not to post as fail memtest when you push it to hard.
If/when it will not post, reset the BIOS and restart.
After you think everything is stable, test overnight with memtest to be sure.
I thought it would be faster to start from unstable and work your way back It only took me about 30mins to tighten my timings I mean sure i haven't stress tested but nor have i found any problems with my rig in the last few months since i did it.