AM2/Core 2 Duo Latency and Memory Bandwidth

The introduction of AM2 merely increased the AMD latency advantage. AM2 latency was slightly lower than DDR latency on AMD.

Memory Latency Comparison - Conroe & AM2

However, Core 2 Duo did what most believed was impossible in Latency. One of AMD's advantages is the on-processor memory controller, which Intel has avoided. It should not be possible to use a Memory Controller in the chipset on the motherboard instead and achieve lower latency. Intel developed read-ahead technologies that don't really break this rule, but to the system, in some situations, the Intel Core 2 Duo appears to have lower latency than AM2, and the memory controller functions as if it were lower latency.

Memory Bandwidth

The other part of the memory performance equation is memory bandwidth, and here you may be surprised, based on Conroe's performance lead, to see the changes Core 2 Duo has brought. Results are the average of ALU/FPU results on Sandra 2007 Standard (Buffered) memory performance test. We used the same memory on all three systems, and the fastest memory timings possible were used at each memory speed.


The results are not a mistake. In standard memory bandwidth, Core 2 Duo has lower memory bandwidth than either AM2 or Intel NetBurst. It is almost as if the tables have turned around. AMD had lower bandwidth with DDR than Intel NetBurst, and the Athlon64 outperformed Intel NetBurst. Now Conroe has the poorest Memory Bandwidth of any of the three processors, yet Conroe has a very large performance lead. It appears Conroe, with shallower pipes and an optimized read-ahead memory controller to lower apparent latency, makes best use of the memory bandwidth available.

Perhaps the most interesting statistics are that the huge increases in memory bandwidth brought by AM2 make almost no difference in AM2 performance compared to the earlier DDR-based Athlon64. With this perspective let's take a closer look at DDR2 memory performance on AM2 and Core 2 Duo. This will include as close to an apples-to-apples comparison of Core 2 Duo and AM2 as we can create.

DDR/NetBurst Memory Bandwidth and Latency Memory Test Configuration
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  • HSuke - Thursday, July 27, 2006 - link

    quote:

    This fact will make our memory testing much simpler, and we plan to perform all upcoming memory testing on the currently more flexible Core 2 Duo test platform. AM2 buyers can expect similar results with the same DDR2 memory on their AM2 motherboards.


    I hope this means that you're going to do the tests on the Core 2 Duo test platform IN ADDITION to your current platforms.

    I hope this does NOT mean that you're going to do the tests EXCLUSIVELY on the Core 2 Duo test platform.



    So are you going to stop doing memory tests with AMD processors? How scientific is that? If you go to page 7 and look at the performance charts, you'll see that memory speeds have a much greater impact (pertage-wise) on the AMD setup than the Core 2 Duo setup.

    Well, I'm quite surprised that memory even made a difference. But since that is true (according to your tests), shouldn't be testing on AM2 instead of Core 2 Duo processors in the future because the difference is more marked? If there wasn't any significant difference on an Intel system, but a significant difference on an AMD system, you'd probably suggest that memory doesn't make a difference, commiting a type 2 error.

    Now, I don't care about memory. I always buy whatever is on sale. But making that conclusion would just piss off so many memory enthusiasts and memory sellers. And aren't those guys the ones that would be reading this article?

    Think about it.
    Reply
  • Wesley Fink - Friday, July 28, 2006 - link

    As we explained in the article, AM2 currently does not support the DDR2-1067 speed, while the Intel chipset for Core 2 Duo DOES support 1067. Since most memory we test can reach 900 to 1067 or 1100 or greater the 1067 ratio is an advantage. Also the current AM2 memory controller does not support settings of 2 for Ras-to-Cas or tRef - AM2 only supports to 3. Core 2 Dupo supports faster timings of 2 at these settings. Since these lower settings are often usable in fast memory they can be very important.

    For these reasons, we will be using the Core 2 Duo platform for testing DDR2 memory, since we can test more of the options that are available and may be important on high-performance DDR2 memory. If and when AM2 upgrades their DDR2 memory controller we will reconsider testing on AM2.
    Reply
  • Kiijibari - Wednesday, July 26, 2006 - link

    Hi everybody,

    first of all I have to admit that this is the best Anandtech article for a long time. Everybody blamed me for being an AMD fanboy latley, however I do not have any problems to admit that Core2 is faster.

    If Intel would not have anything faster than AMD after 3 years of AMD lead, Intel would be best adwised to stop making CPUs and become an AMD chipset company ;-)

    I have one question left: Which BIOS version did you use with the AM2 board ?
    I recoginzed that DDR2 bandwidth scores increased quiet much compared to the initial tests. Now we have Sandra scores around 9.3 GB/s, however I remember that the initial ones were around 7.4 GB/s max.

    In conclusion I assume that there is some optimization going on, due to bios seetings.

    There was also a little test over at lostcircuits:
    http://www.lostcircuits.com/motherboard/foxconn_c5...">http://www.lostcircuits.com/motherboard/foxconn_c5...

    There the Asus board scored just ~7 GB/s, but a tested Foxconn board is again in the 9GB/s area.

    It maybe that the BIOSes are optimized for different kind of RAMs, too, as lostcircuit used OCZ memory, not Corsair.

    Anyways, I think the results are interesting enough to dig a little bit further ;-)

    Thanks again for the great review.

    regards

    Kiijibari

    Reply
  • Wesley Fink - Wednesday, July 26, 2006 - link

    P5W-DH Deluxe BIOS is 701, dated 7/08/2006. The Corsair memory used in this review can do 4-3-4-11 timings at DDR2-1067, where most high-end DDR2 can only reach 4-4-4 timings at that speed. Reply
  • Kiijibari - Wednesday, July 26, 2006 - link

    Sorry, looks like you misunderstood me, I was wondering about the AM2 platform bandwidth results @2.8Ghz and DDR2-800(page3). The Core2 scores are the same as "usual" ;-)

    So can you also say which bios you were using for the Asus M2N32-SLI ?

    thanks a lot

    Kiijibari
    Reply
  • Gary Key - Thursday, July 27, 2006 - link

    quote:

    So can you also say which bios you were using for the Asus M2N32-SLI ?


    0603 - 6/29/06
    Reply
  • OcHungry - Wednesday, July 26, 2006 - link

    But I dont understand why you need DDR2 800 or 1000?
    DDR2 667 w/ tighter timings can run @ 333 1:1 ratio (333x9 for FX62).
    Tell me what I am missing here?
    Reply
  • zsdersw - Thursday, July 27, 2006 - link

    quote:

    I dont understand


    Understatement of the year.

    Reply
  • zsdersw - Wednesday, July 26, 2006 - link

    quote:

    Intel would be best adwised to stop making CPUs and become an AMD chipset company ;-)


    Interesting notion. If it ever came to be, you can kiss price cuts (and innovation) on AMD chips goodbye.
    Reply
  • Shizen - Tuesday, July 25, 2006 - link

    Intel Core 2 comes out and AMD slashes prices across the board... the months ahead look like a great time to buy a new rig! Finally, I can retire my aging 2.8GHz Northwood and move on to PCI-E and DDR2. *_*

    Many thanks to the AnandTech dudes for keeping us abreast with the CPU wars, and I personally hope you guys come out with more articles geared for the midranged ($1000-$1500) buyer.

    Yeah, I like the idea of being a PERFORMANCE fanboi rather than a brand-centric one. o_o
    Reply

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