Question about RAM timings when overclocking.

[Pez D Spencer]

Im still pretty new to overclocking but I've learned quite a bit so far. I haven't actually got into doing any yet because I'm still waiting on my case to arrive. When I do get my system built I will have an Asus A8N32-SLI, Opteron 170, and 2GB Corsair XMS PC3500.

My question is about changing the ram timings when overclocking. Many of the tutorials I have read say that you should "loosen your RAM timings" and I understand what it means to loosen your timings (i.e. increase the numbers) but what I don't understand is what numbers you actually use? Do you just arbitrarily choose a higher number? For example, the XMS I have is two 1GB sticks running at 2-3-2-6. If I need to loosen these timings up then what timings should I choose?

Thanks for any info.

I also posted a thread about the BIOS options on the A8N32-SLI on this forum as well as a few other overclocking forums but nobody seems to have answers. If anyone wants to hop over there and maybe see if you have any info on that it would be much appreciated.

Heres the link to the other thread:
http://forums.anandtech.com/messageview.aspx?catid=28&threadid=1780882

Thanks again.

 

[CalvinHobbes]

If you google for topics like memory latency or go to the memory manufacturers site you should find some info on what the numbers mean. That should help you determine what to do.

 

[GuitarDaddy]

The first number is by far the most important, and usually the first one that you have to increase. And it's been proven pretty conclusively the 7 works best for the last number on AMD's

With your ram the first looser step would be 2.5,3,3,7

However I have found through testing that the best scores are usually achieved by using a divider(keeping speed around 200) and keeping the timings as tight as possible.

Overclocking ram on the A64 platform gives very little performance increase, and the little bit of performance you gain with higher mhz is negated by the looser timings.

About the only apps that seem to benifiet from o/c'd ram are sythetic benches like Sandra memory bandwidth, SuperPI, and to a lessor extent 3dmark. For real world apps and games there is almost no difference.

 

[keldog7]

Theres a good explanation on the DFI forums which outlines in great detail the various RAM timings, and how much "gain" in performance can be expected from each of the timings. I can't seem to find the exact link though... however, a similar thread can be found at:
http://www.hardforum.com/showthread.php?t=760374&page=1

To really know the effect of any change in timings, you should really just benchmark them. SiSoft will do a more than adequate job. Of course, this process is a bit lengthy, if you consider that you wil FIRST want to verify *stability* at a ceratin speed and timing of your RAM. Most folks would probably say that running MemTest86+ for 8 consecutive hours without error is enough to call something stable... But its still 8 hours of testing PER CONFIGURATION.
If you read my signature, you'll see that my rig is very similar to yours (directed at Pez D). I researched that RAM extensively before buying, and was rewarded once it was installed... At 2.7V vDIMM, this ram will overclock beautifully to 250MHz (on a 1:1 divider), with stable timings of 2.5-3-2-7, and 1T command mode!! Put a decent heatsink on that 170, push vCore to 1.425V or so, drop the HTT multiplier to 4x, and increase the bus speed from 200Mhz to 250Mhz, and all of a sudden you have a 2.5GHz Opteron, with RAM running at the same speed as the bus... a nice, simple, 25% overclock.
Best of luck,
A

 

[Pez D Spencer]

Thanks a ton for the info.

 

[ribbon13]

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