Memory timings: Are there optimal combinations?

[jrichrds]

Which settings can be changed individually, and which settings should always be changed in conjunction with other settings?

I've read that there are so-called optimal combinations for memory timings, and that lower isn't always better (for tRAS and tRC if I remember correctly?).

My Corsair DDR2 memory's SPD for 800Mhz is 5.0-5-5-15-18-22
If I want to run it at faster timings, which settings (or combination of settings) should I try first?

 

[tcsenter]

The optimal memory timings are defined by the SPD.

 

[n7]

This is a basic guide i ran across today on another forum.

http://alexanderhuzar.angelfir.../files/ram_timings.htm

A while ago, i tested with low vs. high tRAS when i had Team Xtreem that could run as low as tRAS 4 (4-4-4-4).
In SuperPi, lower tRAS was a tiny bit faster.
In everything else, it was a bit slower once i went much lower than the standard equation explained in that link.

As for what you should try first to increase performance?

Speed.

I don't know if you OC, but first priority should always be CPU.
Once you've attained/determined your CPU's max speed, you try to find the best possible corresponding RAM ratio/frequency/timings.

Generally speaking, it's always speed > timings for pretty much all Intel chipset systems, so you'd actually want to try overclocking your RAM as far as you can.
Then work on tightening timings.

Post your system specs/overclock, etc, & i'll give some pointers.


Just for an example of how i do things:
I run DDR2-800 4-4-4-12 RAM.
Obviously, you can see my sig...i don't run it at that speed or timings, as that would be slower than what i have it at now.

 

[chuckm]

Originally posted by: n7
This is a basic guide i ran across today on another forum.

http://alexanderhuzar.angelfir.../files/ram_timings.htm

Thanks for that great link n7! Should be a sticky.

 

[jrichrds]

Originally posted by: n7
As for what you should try first to increase performance?

Speed.

I don't know if you OC, but first priority should always be CPU.
Once you've attained/determined your CPU's max speed, you try to find the best possible corresponding RAM ratio/frequency/timings.

Generally speaking, it's always speed > timings for pretty much all Intel chipset systems, so you'd actually want to try overclocking your RAM as far as you can.
Then work on tightening timings.

Post your system specs/overclock, etc, & i'll give some pointers.


Just for an example of how i do things:
I run DDR2-800 4-4-4-12 RAM.
Obviously, you can see my sig...i don't run it at that speed or timings, as that would be slower than what i have it at now.

Thanks for the tips n7!

I am running an E7200 @ 3.16Ghz by way of BSEL Select 1333Mhz. I replaced the Corsair with some OCZ PC2-6400 with the following SPD:
JEDEC 1.8V 400Mhz: 5-5-5-15-23
EPP 2.0V 400Mhz: 4-4-4-15 1T (tRAS not defined)

I went straight to speed as you recommended. With CAS 5, the highest speed I can achieve is 933Mhz (466.7Mhz x2, 5:7 ratio). With memory timings set to auto in BIOS, the timings are: 5-5-5-17-27. I decreased it to 4-4-4-17-27 and to my surprise, it still works.

1. Should I play with tRAS and tRC, or does the motherboard know best?
2. Is it worth increasing to CAS 6 and see if the speed will go even higher?
3. What memory benchmark do you use? I have been using Everest Memory and Cache Benchmark.

 

[n7]

Exact specs please...i don't know if you are running 2x1 GB, or 2x2 GB?
What about motherboard?

I assume 2x1 GB, as 4-4-4 @ DDR2-933 with 2x2 GB is highly unlikely.

I don't know your mobo, but you should have higher ratios than you've mentioned.

333 MHz FSB 2:3 = DDR2-1000
333 MHz FSB 5:8 = DDR2-1066

If your RAM is doing DDR2-933 4-4-4 stably, it shouldn't have much trouble hitting DDR2-1000+ 5-5-5.

 

[jrichrds]

Originally posted by: n7
Exact specs please...i don't know if you are running 2x1 GB, or 2x2 GB?
What about motherboard?

I assume 2x1 GB, as 4-4-4 @ DDR2-933 with 2x2 GB is highly unlikely.

I don't know your mobo, but you should have higher ratios than you've mentioned.

333 MHz FSB 2:3 = DDR2-1000
333 MHz FSB 5:8 = DDR2-1066

If your RAM is doing DDR2-933 4-4-4 stably, it shouldn't have much trouble hitting DDR2-1000+ 5-5-5.

2x1GB on ECS GF7050VT-M motherboard with nVidia Geforce7050/nForce610i chipset. Chipset only capable of single channel. Max DIMM voltage in BIOS is 2.0v.

The next step up from 933Mhz is 952Mhz, which causes BSOD in Windows even at 5-5-5. Also had tried 1000Mhz 5-5-5, which causes BSOD during Windows boot.

 

[n7]

Eh...that mobo isn't going to be so hot for OCing obviously.

Since the higher ratios aren't stable, then you are a bit more limited for choices.

I'd say try tightening up timings as much as you can at your current speed then