4 DS DIMMs at 1T: Memory Stress Testing

The DFI easily handles 2-2-2-7-1T timings at stock speed with 2 double-sided dimms, as do almost any of the current boards for AMD Socket 939 from NVIDIA, SiS, VIA, and ULi. However, what is truly unique is that the DFI LANParty UT RDX200 is the first board designed to run four double-sided 512MB or 1GB DIMMs at the fastest timings and a 1T Command Rate. In fact, AMD specifications tell us that this is impossible. To his credit, Oskar Wu and DFI found a way to accomplish the impossible.

Stable DDR400 Timings - 4 DIMMs
(4/4 DIMMs populated)
Clock Speed: 200MHz
CAS Latency: 2.0
RAS to CAS Delay: 2T
RAS Precharge: 7T*
Precharge Delay: 2T
Command Rate: 1T
*7T was determined by MemTest86 benchmarks to deliver the widest bandwidth with the ATI Rx480/482 chipset. While the board would operate at tRAS of 5T or lower, all benchmarks were run at 7T.

With the ability to run 4 DS DIMMs at 1T, we had the opportunity to finally show the impact of a drop to a 2T Command Rate on performance.

First, for those skeptical that this is possible, we captured screens from the freeware A64 Tweaker and CPU-Z showing operation of 4 DIMMs at 1T.


Click to enlarge.

All the benchmarks below were run with an FX-57 processor and are not directly comparable to our standard benchmarks which use an AMD 4000+ CPU.

To clearly demonstrate the impact of the normal 2T drop in Command Rate on performance, we ran Aquamark3 benchmarks with 2 DIMMs at 1T, 4 DIMMs at 2T, and the new option of 4 DIMMs at 1T.

2 DIMMs at 1T is normally the fastest available option.

You can see that doubling the memory, but being forced to drop to 2T Command Rate, lowers the A3 scores by over 1,000 points.

The surprise, however, is the new DFI option of 4DS DIMMs at 1T. Not only is there no performance loss - the scores are 2,000 points higher than 4DSx2T - but 4DS DIMMs at 1T outperforms 2x1T by almost 1,000 points. This makes 4DS DIMMs at 1T in the DFI to be the new performance leader at stock speeds.

For those who are thinking that surely there's a catch, the answer is "yes, there is". 1T operation is only possible to a frequency of about DDR406, which basically limits it to stock speeds. Above that speed, you must run 4 DS DIMMs at 2T as you normally must. However, at or near stock speeds, the 1T option is a brilliant development that delivers better performance.

Overclocking: DFI LANParty UT RDX200 Test Setup
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  • bigtoe36 - Tuesday, October 18, 2005 - link

    having tested the RDX200 at the same time as Wesley I am able to confirm that i was able to run cas1.5. Now on the NF4 LP boards oskar enabled what seemed to be cas1.5, infact this option gave no performance increase over the cas2 option. On RDX200 he has though found a significant speed increase by using the 1.5 option.

    Running OCZ PC4800Plat's with drive srength at 9 and 1.5-2-2-5 timings a 100MB/s increase in available memory bandwidth was seen over setting 2-2-2-5. I was however forced to use 3.1Vdimm to achieve this at 200fsb 1:1. Another point is that BH5 and VX (UTT CH5) would not do cas1.5, it seems to be a samsung TCCX tweak only.

    Reply
  • mongoosesRawesome - Tuesday, October 18, 2005 - link

    thanks for the info Reply
  • Leper Messiah - Tuesday, October 18, 2005 - link

    Used to be buy an nVidia mobo and an ATi graphics card. Funny how things have changed...but 4DS at 1T is awesome if you aren't OCing your RAM, but 250-2-2-2-7 2T is going to be faster than 203 2-2-2-7-1T. Reply
  • Madellga - Tuesday, October 18, 2005 - link

    Thanks for the good review Wesley. One thing I always missed on your reviews was what kind of BIOS settings you used.

    It took me a long time to get my DFI-NF4 up and running. You know better than anybody that tweaking is time consuming - specially with so many settings on the BIOS.

    Make this an habit and keep posting the BIOS settings used on the reviews.
    Reply
  • mongoosesRawesome - Tuesday, October 18, 2005 - link

    quote:

    A good example of this is the options available for memory speeds at stock speeds. Not only can you choose 200, 266, 333 and 400, but you can choose and fine tune with in-between speeds like 240, 280, and 300. Beyond the standard 400, you can choose 433, 466, and 500. This allows those who would never think of overclocking their CPU the ability to run their memory at DDR500 for example. For those who do overclock, this increases the ability to fine-tune the CPU and memory for the absolute best performance.


    Isn't that integrated into the A64 memory controller and don't the Nforce 4 DFI boards support those DDR speeds?
    Reply
  • Wesley Fink - Tuesday, October 18, 2005 - link

    The additional ratios are available in the AMD Athlon64 Rev. E Memory Cntroller and can be implemented on any Socket 939 motherboard. However, the BIOS writer has to implement these choices. AMD made them a part of their Reference Board and they will likely find their way to many retail boards. DFI implemented them on the RDX200, but you rarely if ever see these finer ratios actually implemented on nForce4 boards. Reply
  • jr9k - Tuesday, October 18, 2005 - link

    quote:

    The surprise, however, is the new DFI option of 4DS DIMMs at 1T. Not only is there no performance loss – the scores are 2,000 points higher than 4DSx2T. (...)


    2000 points.
    Impressive...
    until you do some math. 4 dimms at 1T are 2.3% faster than 4 dimms at 2T.

    Don't get me wrong, the achievement of running four dimms at 1T is impressive, but the results are not (as we already knew). It's the way of showing things.

    Anyway, it is good to see some competition from ATI.

    Nice review and nice board
    Reply
  • mongoosesRawesome - Tuesday, October 18, 2005 - link

    Yea, I agree. A lot of times a big deal is made over only a few percentage points. I would have rather seen FPS in some games. I truly doubt we'd even see 2% in some cases. Reply
  • Spacecomber - Tuesday, October 18, 2005 - link

    I had the same sort of reaction to the signifigance of the 1T vs 2T scores. I translated the Aquamark score back into FPS got this.

    2 DIMM 1T 91fps
    4 DIMM 2T 90fps
    4 DIMM 1T 92fps

    While this capability certainly says good things about DFI's engineering team, I'm not sure that I'd spend a $100 premium on a motherboard just to get this feature.

    Overall, this is a board with very good potential, but I wouldn't want to rush out and buy this first release. It sounds like the revision with a different south bridge will be worth waiting for. Hopefully, the price will be mroe in line with the comparable nforce4 boards by then, too.
    Reply
  • ksherman - Tuesday, October 18, 2005 - link

    I am particularly impressed with the ability to use 4DS DIMMs @ 1T. That is a really nice little feature! Too bad you have to stay near stock speeds... is it possible to do some overclocking, but use divides to keep the memory at 406? or is overclocking the memory the better thing to improve system performance? Reply

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