Mysterious RAM timings (TRFC, TRRD, etc.)


Jan 7, 2007
For my motherboard (ASUS P5B Deluxe), I can set a lot of timing values. The first four are discussed in the FAQ here, and are advertised by my RAM provider as 4-4-4-12:

CAS (called "CAS# Latency" in my BIOS)
tRCD (RAS# to CAS# Delay)
tRP (RAS# Precharge)
tRAS (RAS# Activate to Precharge)

But I also have access to the following settings; what are they? How can I find out what the values should be set to, aside from running Memtest zillions of times?

Write Recovery Time
Rank Write to Read Delay
Read to Precharge Delay
Write to Precharge Delay

I'm using 5-35-10-10-10-10 for now, but I think 5-35-3-10-5-13 might work. My Memory is 2x1 GB OCZ Platinum DDR2-800 PC6400 4-4-4-12.

Edit: according to CPU-Z the SPD has 5 values (5-5-5-15-22). I think the last, large value might be TRFC, but for TRFC I can't even use a value of 30 or below without instability.


A good guide

DRAM TRFC simple rule for this option. If your memory is Micron IC based you may be able to go as low as 20, everything else we have found 35 works best. Options are 20 25 30 35 and 42. obviously 42 is very lose and will allow higher overclocks.

TRRD Options 0 to 15, around 10 is where most leave this, no big effect on performance.