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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  • zsdersw - Tuesday, July 25, 2006 - link

    I care about people making blatantly false claims. Reply
  • Wesley Fink - Tuesday, July 25, 2006 - link

    We used the SAME memory timings on both processors if they were available. For the DDR2-1067 and DDR2-800 they were exactly the same on both processors in all tests, which is why they were used for our 2.93GHz comparison. At DDR2-667 and below, the Core 2 Duo could support timings like 3-2-2, where AM2 only supports 3-3-3. This article was to evaluate memory performance, so we did everything possible to keep all variables the same.

    Memory timings were DDR2-400 - 3-2-2-5; 533 - 3-2-2-6; 667 - 3-2-3-7; 800 - 3-3-3-9; 1067 - 4-3-4-11; DDR2-1112 - 5-4-5-14.
    Reply
  • duploxxx - Wednesday, July 26, 2006 - link

    well those cas settings were to be expected when you saw the memory performance chart.
    you just killed the performance after ddr2 800 cas4 is ok but the minor step you have from ddr 1067 to ddr 1112 and again 1 cas higher is the end of good performance. so the memory of the fx to get to 2.9 was? that explains probably the lower performance vs the linear performance increase in the memory.....
    Reply
  • Bingo13 - Wednesday, July 26, 2006 - link

    quote:

    you just killed the performance after ddr2 800 cas4 is ok but the minor step you have from ddr 1067 to ddr 1112 and again 1 cas higher is the end of good performance.


    The timings utilized by AnandTech were about the best you will see with current DDR2 memory. They did not kill the performance, the memory capability is what limited the testing. Tell me, where can you buy DDR2 that will do 3-3-3-9 at 1067. This review was more than fair in the settings it utilized for the tests and it took $450 memory to do it.
    Reply
  • duploxxx - Thursday, July 27, 2006 - link

    yes i know but you don't get my point...
    we know fx34 will be 3.0 so its stupid to try and get an fx at 2,93.
    run an fx at 3.0 (multiplier change) with the nice cas3-3-3 like you did and the performance will be way better. now you killed the performance (speedbump cpu and memory) by dropping the cas to 4
    Reply
  • Wesley Fink - Wednesday, July 26, 2006 - link

    DDR2-800 was 3-3-3-9 2.2V. The FX at 2.93GHz was running DDR2-1067 at 4-3-4-11 2.2V. Reply
  • Gary Key - Tuesday, July 25, 2006 - link

    We had a slight change in pages after the article went live. Page seven now represents stock memory performance on each platform with page eight now showing the overclocked FX62 (11x266, 2.93GHz) compared to the X6800 (11x266, 2.93GHz). A comparison that is quite revealing based upon numerous comments about what the expected results of running a high memory strap and low latency settings on the AM2 platform would even out the performance differences between the two platforms. Reply
  • Wesley Fink - Tuesday, July 25, 2006 - link

    We were moving pages around as it posted. The page references should now be correct. The page that AMD fans will likely hate is now page 8. Reply

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