AMD AM3 Memory Speed vs NB Speed

From OCZ Forum Wiki

With popularity growing for AM3 and people looking to squeeze every last drop of performance from their Black Edition CPU i though i would investigate the best way to set up a system and see just which method of running the memory was faster.

Most feel higher numbers = better, so 1600MHZ ram should be better than 1333MHZ ram...prepare to be shocked and pleased all at the same time!

The key to Phenom 2 performance is the NB clock or memory controller clock, it is shown in the bios on most boards as CPU-NB or memory controller and has its own multiplier adjustment all of its own.

Stock speed is 2000, but this is FAR FROM BEST...you really do need to consider 2600MHZ or higher for you to get the best from your system. So lets see my results and i will explain where you need to focus your tweaking efforts.

1333 6-6-6-24 1T and 1600 7-7-7-24 1T but with the NB-CPU clock at 2000, 2200, 2400, 2600, 2800 and 3000 with CPU @ 3.8GHZ as this is where the bulk of air and watercooled rigs will land. Tests are super pi 32m and AutoGK encode DVD FILM 720X480 800MB VOB up scaled to 1280x960 AVI 160MP3 sound 350MB file.

time is converted to seconds for both test, lost the decimal places off PI as they were not needed ;)

TEST WITH RAM AT 1333 6-6-6-24 1T

TEST WITH RAM AT 1600 7-7-7-24 1T

1333 RAM RESULTS:

32M pi 35secs faster with NB clock at 3000 over 2000

encode 47secs faster total job NB clock at 3000 over 2000

1600 RAM RESULTS:

32M Pi 36 secs faster with NB at 3000 over 2000

encode 57secs faster total job NB clock at 3000 over 2000

So lets make this easy for you and drop the results on the same graphs ;)

As you see 1333 6-6-6-24 1t is faster than 7-7-7-24 1t for super Pi but slightly slower for encoding. What you need to note though is at around 2400MHZ CPU-NB encode test both 1333 and 1600 are so close its not worth bothering about...after that 1600 is faster as 1333 memory starts to become a bottleneck.

Update May16th 1:25AM...5-5-5-24 1t hits back. you guys looking for 1800MHZ ram at 8-8-8- or 9-9-9- forget it, with the NB around 2400 to 2800MHZ 5-5-5-24 1t 1333 is where you need to be.

And finally adding 6-6-6-24 1t 1600MHZ into the graph...for me 1333 5-5-5-24 1t is best, easier to do with most ram and for me allowed an easier OC on the CPU and the CPU-NB.

Moving on now we have a another domain we can overclock called HT let us see how overclocking this has an effect on 3D performance. 3870X2 Video card, stock clocks. 3dmark vantage CPU @ 3.8GHZ, CPU-NB@ 3GHZ, RAM @ 1600 7-7-7-24 1t

As you see 2000HT is faster by a mile than 2600HT so leave it at stock speeds...no tweaks needed ;)