About 7 months ago I posted data comparing two memory dividers (1:1 and 3:5 @ 333 MHz) on my then Q6600/P965 based system and concluded that for the 67 % increase in memory bandwidth, the marginal gains in actual performance weren't worth the extra voltage/heat.

Since then I've upgraded my hardware to an X3360/P35 setup and wanted to revisit this issue. Again, two dividers were looked at: one pair running 8.5x333=2.83 GHz, and another running @ 8.5x400=3.40 GHz:

333 MHz FSB:
1:1 a.k.a. PC2-5300 (667 MHz)
5:8 a.k.a. PC2-8500 (1,067 MHz)

400 MHz FSB:
1:1 a.k.a. PC2-6400 (800 MHz)
4:5 a.k.a. PC2-8000 (1,000 MHz)

I figured there would be a much greater difference in the 333 FSB case since the memory bandwidth increased by 60 % vs. 25 % in the 400 MHz FSB case. All other BIOS settings were held constant with the exception of the divider (and the strap) and the given FSB. Subtimings were set to auto and as such could vary as managed by the board which I found out, was required since manually settings some of the subtimings lead to either an incomplete POST, or an unstable system.

The benchmarks were broken down into three categories:
1) "Real-World" Applications
2) 3D Games
3) Synthetic Benchmarks

The following "real-world" apps were chosen: x264, winrar, and the trial version of Photohop CS3. All were run on a freshly installed version of Windows XP Pro x64 SP2 w/ all relevant hotfixes. The 3D games were just Doom3 (an older game) and Crysis (a newer game). Finally, I threw in some synthetic benchmarks consisting of the Winrar self test, Super Pi-mod, and Everest's synthetic memory benchmark. Here is an explanation of the specifics:

Trial of Photoshop CS3 – The batch function in PSCS3 v10.0.1 was used process a total of fifty-six, 10.1 MP jpeg files (226 MB totally):

1) bicubic resize 10.1 MP to 2.2 MP (3872x2592 --> 1800x1200) which is the perfect size for a 4x6 print @ 300 dpi.
2) smart sharpen (120 %, 0.9 px radius, more accurate, lens blur setting)
3) auto levels
4) saved the resulting files as a quality 10 jpg.

Benchmark results are an average of two runs timed with a stopwatch.

RAR version 3.71 – rar.exe ran my standard backup batch file which generated about 955 MB of rars containing 5,210 files totally. Here is the commandline used:

where list.txt a list of all the target files/dirs included in back up set. Benchmark results are an average of two runs timed with a stopwatch.

x264 Benchmark HD – Automatically runs a 2-pass encode on the same 720p MPEG-2 (1280x720 DVD source) file four times totally. It contains two versions of x264.exe and runs it on both. The benchmark is the best three of four runs (FPS) converted to total encode time.

Shameless promotion --> you can read more about the x264 Benchmark HD at this URL which contains results for hundreds of systems. You can also download the benchmark and test your own machine.

3D Games Based Benchmarks

Doom3 - Ran timeddemo demo1 a total of three times and averaged the fps as the result. Settings were 1,280x1,024, ultra quality with 8x AA.

Crysis - Ran the included "Benchmark_CPU.bat" and "Benchmark_GPU.bat" both of which runs the pre-defined timedemo, looped four times. I took the best three of four (average FPS) and averaged them together as the benchmark. Settings were 1,024x768, very high for all (used the DX9 very high settings hack, and 2x AA.

"Synthetic" Application Based Tests

WinRAR version 3.71 – If you hit alt-B in WinRAR, it'll run a synthetic benchmark. This was run twice (stopped after 150 MB) and is the average of four runs.

SuperPI / mod1.5 XS – The 16M test was run twice, and the average of the two are the benchmark.

Everest v4.50.1330 Memory Benchmark - Ran this benchmark a total of three times and averaged the results.

Hardware specs:

Note: the performance levels (tRD) are set automatically by the board which wouldn't POST if I manually tweaked them. Even though they're different, I still feel the data are valid since this is the only way I can run them. In other words, if I'm going to run the higher dividers, it'll be as such or it won't POST!

Without further ado, here are the data starting first with a 333 MHz FSB comparing the 1:1 vs. 5:8 divider (DDR2-667 vs. DDR-1066):


Here are the averaged data visualized graphically:


Now on to the 400 MHz FSB comparing the 1:1 vs. 4:5 divider (DDR2-800 vs. DDR2-1000):


And graphically:


As you can see, there way nothing spectacular in either the real-world category, or the 3D games category in comparison to the massive increase in memory bandwidth (shown on the graphs in red). In fact, I was surprised to see that there were really no gains by Doom3 and minimal gains by Crysis. This is probably due to the fact that the video card shoulders the burden of these games with Doom3 being the light-weight of the two. As expected, the synthetic benchmarks did pick-up on the larger bandwidth, but only in the case of the 400 MHz FSB did I see anything approaching the theoretical increase (14 % of 25 % vs 15 % of 60 %).

If you read my first memory bandwidth post, perhaps the same conclusions can be drawn from these new data. One thing I'll add is that this new MB doesn't require extra voltage like my older P5B-Deluxe did to run the higher dividers, so it's not producing that much more heat. That said, I'm actually running the system with the 4:5 divider, since things seem to feel faster to me (windows opening, responsiveness, etc.) which are all unfortunately intangibles I can't measure.

Thanks as always, graysky. Much appreciated.

I think I remember that you did a test with different FSB speeds but same cpu speeds. Could you do that test again with your newer system? I don't think anything has changed, but it's always good to know.

Cheers!

@evilonigiri - maybe later dude... I'm pretty burnt out of tests after this one.. they are pretty tedious and time consuming as you can imagine

Of course. I did some tests with the PCI-E frequency before and that was quite tiring.

And of course, I would be referring to this in the future. You have my thanks again.

very nice

thanks for your hard work.

I edited the first post switching the highest 400 MHz FSB run from 5:6 to 4:5 (960 MHz vs. 1,000 MHz) and included some info about subtimings to make things more clear.

Great Post.. Interesting.
Would like to see something similiar but with the memory timings optimized. Unfortunately it sounds like you had a problem there.
Currently running my memory 1:1 at 667mhz (underclocked), but the timings are 3-3-3-8 1T. I wonder how it would compare to higher mhz with looser timings. Like 800mhz 4-4-4-12 2T, or even 900+ mhz.

Yeah, good question. I haven't tried backing off on the main timings with these chips.