Memory Test Configuration

When the article on AM2 processor performance was published a few days ago, the highest performance that could be reached with stability was DDR2-800 at 4-5-4 timings. A new BIOS will now allow the OCZ PC2-8000 reviewed in OCZ EL PC2-8000 XTC: Low Latency PLUS DDR2-1100 to run at 3-3-3 timings in AM2 prototype motherboards. This matches the highest performance achieved with this memory at DDR2-800 on the Intel 975x platform and allows a better comparison to fast DDR-400 memory on the AMD Socket 939 platform.

Pictures of the motherboards used for testing and/or photos of the AM2 processors tested might compromise our product sources, so there will be no pictures with this article. We can tell you that we now have several AM2 motherboards of very recent chipset updates along with several earlier boards that perform at a lower level. We are also testing our 4th spin of AM2, released days ago, and we have also seen increased performance with each spin of the AM2 CPU.

The design of the test bed is to assure, as much as possible, that the only difference between 939 and AM2 test systems is in the memory subsystems. This includes using the latest FX-60 X2 processor with the most recent DDR memory controller adjusted to the same speed as the AM2 X2 processor. Both motherboards are also based on similar NVIDIA chipsets, and all testing was done with the same Hitachi 200GB hard drive using the same OS installation. The MSI 7800GTX video card was used for testing in both systems. We also had NVIDIA 7900GTX and ATI X1900XT video cards available for testing, but we used the 7800GTX for easier comparison to results from other recent motherboard and memory reviews.

System Configuration
Processor: AMD AM2 X2
AMD FX-60 (X2) adjusted to match AM2 processor speed
RAM: OCZ EL PC2-8000 XTC (DDR2-1000, 2x1GB)
Crucial CLIII5N.32 PN56278 (DDR-500, 2x1GB)
Hard Drives: Hitachi 200GB SATA2
Video Card: MSI 7800GTX 256MB
Video Drivers: NVIDIA ForceWare 84.21
Power Supply: OCZ PowerStream 520W
Operating System: Windows XP Professional SP2
Motherboard: Pre-Release AM2 motherboard based on NVIDIA chipset
Asus A8N32-SLI Deluxe


While the speeds of top DDR and DDR2 are different, we tried to match other factors within memory as much possible. Both DDR and DDR2 were 2 GB kits consisting of 2x1GB dimms. DDR was top-line DDR500 tested at the fastest DDR400 2-2-2 timings; DDR2 was top-line DDR2-1000 tested at the fastest DDR2-800 3-3-3 timings. DDR memory that performs at DDR400 2-2-2 is a premium part and it was compared to a premium DDR2 part.

A more mainstream comparison would have been DDR400 3-3-3 to a DDR2-667 4-4-4 pushed to DDR2-800. The performance differences in the mainstream parts would have been similar, but they would not really reflect the state of the memory market in about 6 weeks. We know that all the top memory vendors plan new DDR2-800 high performance and mainstream parts for the AM2 launch, and offerings at the top of mainstream and high-end will be different in a few weeks. The OCZ PC2-8000 we used for testing, however, is a just-launched DDR2 memory based on what is widely expected to be the best performing DDR2 memory chips available for the near future. This top to top comparison should therefore provide a clear approximation of real performance when AM2 launches.

There is always room for some unexpected AMD announcements, but as Anand explained in his article about the April spin of AM2: ". . . according to internal AMD documents, AM2 CPUs are going to start being sold to distributors starting next month, leaving very little time for significant changes to the CPU to impact performance. We feel that now is as good of a time to preview AM2 performance and put things into perspective as we're likely to get before the official launch." We all can hope for a surprise from AMD, but with distributors receiving parts in less than a month and with official launch just 6 weeks away, we are probably testing what is very close (if not identical) to the final AM2 part.

Index Socket 939 Fast DDR-400 vs. AM2 Fast DDR-2
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  • peternelson - Saturday, April 15, 2006 - link


    I notice all your tests were performed in 32 bit mode.

    This cpu can handle 64 bit instructions.

    While 64 bit registers (and more of them) allows faster data manipulations, that advantage is traditionally offset by the need for bigger wordsize of instructions.

    So if the memory reading of the instructions is more memory-hungry that could be more use for this extra memory bandwidth.

    Therefore I suspect IN 64 BIT MODE, there could be more advantage on a fast DDR2 than on a bandwidth-limited DDR system.

    How to test this? Well you could run some 64 bit Windows and BENCHMARK FAR CRY in 64 bits version as it is available as 32 and 64 bit.

    See if running in 64 bit with this new ddr2 memory negates the disadvantage of limited bandwidth for instruction feeding?

    If so this would be increasingly an advantage in future as more people move to 64 bit OS, including at Vista-time.
    Reply
  • smitty3268 - Saturday, April 15, 2006 - link

    The larger instruction size is barely an issue. The real difference is that all pointers are doubles in size from 32 to 64 bits. This can lead to a significantly lower number of variables stored on the cache, which can lead to increased bandwidth usage. Reply
  • AnandThenMan - Saturday, April 15, 2006 - link

    I agree with what you are saying. In 64 bit mode, that A64 *should* benefit from the increased DDR bandwidth.

    The problem is, the 64 bit version of Farcry was basically a scam and offered no performance or visual increases solely because it was a 64 bit optimized game. If I remember correctly, the extra visual effects in the 64 bit version were basicially enabled if run in 64 bit mode, but had little or nothing to do with actually being optimized for the A64 in 64 bit mode.
    Reply
  • peternelson - Saturday, April 15, 2006 - link


    I see your point too.

    Yes some additional features could have been done on 32 bit version but were restricted to 64 bit platforms. But surely the compiled binary was actually a 64 bit binary even if not optimised much? In which case it would still be interesting to compare.

    32 bit DDR versus 64 bit DDR and versus 32 bit DDR2 and versus 64 bit DDR2.

    My hypothesis is that the speedup (even if small) from using the 64 bit binary over the 32 will be greater on AM2 DDR2 than the same test on 939 DDR.

    I agree that Far Cry was not the best example, but you may know of other good benchmarks or games which are tuned for this.

    eg the same four tests of PRIME95 (www.mersenneforum.org) which is available in 32 and 64 bit. The Trial factoring test benchmark shows a good speedup in 64 over 32 bit operations. But then that doesn't use main memory much as it is highly optimised to work inside the L1/L2 cache. There must be other suitable tests though to compare 32 and 64 bit on some memory intensive task with binaries optimised for each architecture.
    Reply
  • IntelUser2000 - Saturday, April 15, 2006 - link

    quote:

    My hypothesis is that the speedup (even if small) from using the 64 bit binary over the 32 will be greater on AM2 DDR2 than the same test on 939 DDR.


    Right, the hypothesis for higher clock speed giving better increases were similar, however it gave less increases.


    Wesley, there is another typo. On this page: http://www.anandtech.com/cpuchipsets/showdoc.aspx?...">http://www.anandtech.com/cpuchipsets/showdoc.aspx?...

    DDR400 to DDR2-800 performance increase in CoD2 is said to be 10.6%. That is not correct. DDR400 to DDR2-533 is 10.6%, but DDR400 to DDR2-800 is only 6.7%. Check your calculation numbers please.
    Reply
  • Wesley Fink - Saturday, April 15, 2006 - link

    The calculation has been corrected. Thank you for catching this and bringing it to our attention. Reply
  • peternelson - Saturday, April 15, 2006 - link

    You should not claim AMD's on-processor memory controller is UNIQUE".

    Unique means nobody else does it and it is a unique feature of AMD.

    THAT is incorrect.

    Although Intel don't do it, there are other chips that have on-chip DDR or DDR2 controllers including Clearspeed. I can even put a ddr or ddr2 controller (or several) into my own chip designs in a Xilinx FPGA because Xilinx license the design free for use in their chips.
    Reply
  • Griswold - Saturday, April 15, 2006 - link

    Pretty unique in the x86 world, isnt it? Reply
  • peternelson - Saturday, April 15, 2006 - link


    No, actually it isn't. That was precisely my point.

    Transmeta Efficeon and VIA C7 can both have on die memory controllers too.

    They run x86 instructions quite happily.

    Don't get me wrong, it's a good idea, it's just not UNIQUE any more.
    Reply
  • Wesley Fink - Saturday, April 15, 2006 - link

    Transmeta and the VIA C7 aren't really AM2 and Conroe competitors in most situations. However, I can conceive some applications where they might be. To be more precise I will try to use another word to describe the on-processor memory controller in the future.

    Do you work for VIA or Transmeta?
    Reply

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