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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  • Zebo - Tuesday, July 25, 2006 - link

    Nice one Wes and it makes sense no matter what to have memory testing done on the top dog platform, Conroe.
    Reply
  • Mclendo06 - Tuesday, July 25, 2006 - link

    Is there any reason that either company, Intel or AMD, couldn't design a future processor both with an intelligent pre-fetching algorithm such as is seen in the Core 2 Duo and an on-die memory controller like on the AM2 processors? Seems like the apparent memory latencies could be dropped very significantly by combining these features. Reply
  • Calin - Tuesday, July 25, 2006 - link

    We are hoping in the next big update to AMD processor (the K8L) to have some kind of intelligent prefetching (it is entirely possible, but it costs a number of transistors). Possibly that "intelligent prefetching" means reordering loads from memory, and this happens before the memory controller Reply
  • Ingas - Tuesday, July 25, 2006 - link

    quote:

    Possibly that "intelligent prefetching" means reordering loads from memory, and this happens before the memory controller


    How can Core 2 Duo do prefetch before memory controller?
    I miss some point, do I?
    Reply
  • Calin - Wednesday, July 26, 2006 - link

    I wasn't clear enough. The memory controller gets requests for memory, and returns that memory. Nothing more, nothing less.
    All the logic for preordering is housed in the proper microprocessor, and not in the memory controller - as such, it has no relation with the integrated/discrete implementation of the memory controller.
    Reply
  • vailr - Tuesday, July 25, 2006 - link

    Has anyone run: a Core2 Duo CPU comparison of DDR vs. DDR2, running on the ASrock 775Dual-VSTA? To determine how much slowdown would occur, by using the older DDR memory? Reply
  • Ingas - Tuesday, July 25, 2006 - link

    Interesting point!
    Maybe Core intelligent look-ahead so intelligent, that it even performs equaly on DDR!
    Hm.
    Very interesting!
    Reply
  • Gary Key - Tuesday, July 25, 2006 - link

    We will show this in our review. ASRock just released bios 1.4 that addressed a few issues we noticed in our preview of the board. Reply
  • photoguy99 - Tuesday, July 25, 2006 - link

    ...that AMD is thoroughly owned.

    It's amazing the arguments have still persisted up until now about excuses for Core2 doing so well.

    It was mentioned that AMD survived before at the lower end of the market - but remember how much trouble they had? There were losing money all the time back then. Now they have taken *all* of their 2.5B cash reserve and spent it on ATI. Nice.

    It hurt AMD's credibility even more when Dirk Diggler recently said 4x4 was going to be an answer to Core2. Right. After 30 years of dual socket systems being a niche they are finally going to take off and save you - good luck with that.

    Reply
  • duploxxx - Tuesday, July 25, 2006 - link

    because you have no idea what is going behind the scene and only looking at performance of a desktop cpu and think this is the real world.

    almost no review site is proud enough to get up against the hyping marketing machine from intel. well then believe the marketing hype and own a cpu that has a crapy design when it comes to real multithread and 64bit. way to go to the future knowing vista is comming your way.

    multicore/multisocket is the future, even intel knows it.

    amd is in a much stronger position know and by the end of this year the make procs with a price tag 50% lower than intel intel can only counter this by going to 45nm end of 2007. knowing the cost of all the intel crew, fabs and size of the processors.
    Reply

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