Join Date: Mar 2005
Location: Greater Chicagoland Area
Since you're interested in what does what, here's more info than you probably want:
Refresh Rate (tRFC)
Memory stores ones and zeros as charged and uncharged capacitors,
Billions of them! - a 4 Gig stick has 4.000,000,000 capacitors - arranged in rows and ranks.
A charges capacitor represents a one and an uncharged capacitor equals a zero.
The problem with capacitors is that they slowly loose their charge.
So, periodically memory has to stop whatever it's doing and refresh all the ones and zeros. That takes time.
If it doesn't happen often enough and capacitors loose their charge whatever is stored in memory gets corrupted. (Note, not lost, but corrupted - see below.)
If it happens to often then the memory is wasting time refreshing data when it isn't yet necessary to do so.
When you increase memory voltage you're putting more charge into the charged capacitors, and it takes longer for then to leak down.
To much voltage for to long destroys capacitors.
Refreshing the capacitors more often can be equivalent to increasing voltage. You can run lower voltages at higher speeds with higher refresh rates.
So adjusting tREF can make memory stable and/or increase performance.
But it has to be adjusted just right between to much and not enough time to work the best.
When CAS or many other timings are set to low the memory just stops working, and, usually, the computer just freezes.
So you just reboot, enter the BIOS and change the offending setting.
But, with tREF the memory keeps working, but any data the memory handles gets corrupted.
That most often results in a corrupted OS. The computer becomes a boat anchor until you reinstall - everything.
One easy way to avoid this is to install a second copy of your OS. Your current key will work and you don't need any Windows updates. just a few drivers.
If you use that install to do all your memory tweaking it makes life a lot easier. Once you figure out what you want to do you can set up your memory overclock on your main OS.
Maximum Asynchronous Latency also has a great effect on stability.