1T vs 2T Command Rate - Is there a Real Performance Difference?

The matter of 1T vs 2T gets debated frequently and often with no resolution of an outcome. Many (including myself at times ) have stated that there is a huge or big drop in performance when running 2T over 1T Command Rate timing - but how big is this difference? And for those who can run 4x Memory modules they default to 2T. Are they really missing out on much?

What I have decided to do is to try and help discover what the size of this difference could be by running a series of common benchmarks and tests, record the results and then measure the difference of each run.

The system used was:

A64 3000+ Venice
DFI nF4 DR-SLi (7/04-3)
2 x 6600GT SLI

Memory Timings were kept loose to allow for minimal changes across the DDR range and the actual value of each score is not important here but the differences between each. By keeping these changes between each run to a minimum we are reducing the influences of any other memory tuning.

CAS 2.5-4-4-7

Of the changes made between the individual runs; were the DDR ranging from 200-300 at 1:1 ration and the CPU on x9 multi. A full re-run of the tests were then made changing the Command Rate from 1T to 2T.

The Benchmark Apps used were:

SiSoftware Memory Bandwidth
Everest Home Bandwidth
Aquamark3
3D Mark2001 SE
SuperPi 1M


While I am running these benchmarks what do you think the difference will be?

EDIT:
Summary and Results

Attached is a Zipped PDF with the graphs showing the results of the test.

The Bandwidth tools (Everest & SiSoft) show a significant difference between running 1T vs 2T Command Rate - upwards of 25%, however, the Benchmark tools did not reflect such a large gap and there seems to be about a 2-3% performance hit when running 2T. It would appear that the Bandwidth Tools use some test process which is not reflective of the real world situation and as a result people quote these figures as being the reason not to use 2T timing...

Now if you look across the DDR scale you will see that if you are able to increase DDR by 7-10% this will have effectively reclaimed the 2-3% performance hit of the 2T setting. This is something to consider when trying to get that high OC where maybe 2T is stable but 1T just isn't.

I know that I will now consider 2T for these high OC and see if it helps rather than dismissing it without giving it a go .... Food for thought

@Sphere, let's see of there is alot of interest before it can be a sticky maybe a FAQ. thxs

@Ket, yeah what I am finding is that the Everest and SiSoft tools are showing a gap but does this gap reflect as wide in the benchmarks, hence these test runs

@bigval, good point on the 0T I will try to include this setting across the whole range if possible (which tweak tool are you using to set 0T? A64 has only enable / disable)

@BSman, hopefully today or tomorrow pending 0T outcome...

Cheers

For a much talked about subject throught out a lot of other threads there seems little interest here... is it that the facts may spoil someone's generalised statement ...

Anyway I have completed my tests and will update post #1 with the findings soon, hopefully they will be of interest.

Thank you very much... so the next thing is the CAS ratings which Jack and I are working on together in the background and there will be another thread on that sometime next week.

Hope it all helps.