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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  • Coogcheese - Tuesday, July 25, 2006 - link

    Is the latency issue really due to intelligent look-ahead or the vast cache size difference between the two processors? I'd like to see a benchmark comparison between an 2MB cache opeteron and an equally cached/clocked/timed Conroe. That would settle some debate (yea, yea...wishful thinking).

    It could also help lend some insite to what AMD might do in the short & long term as a response as well.

    The author of the review seems to give alot of credit to "look-ahead" but I found this benchmark comparison to be interesting: http://www.hexus.net/content/item.php?item=6256&am...">http://www.hexus.net/content/item.php?item=6256&am...

    Opteron doesn't seem to have same problem that the Athlon does in terms of latency performance. Which could be why amd execs seem less than panicky at this point. It would allude to a market war similar to the megahurtz war that led to amd coming out with the model # system...this time it could be intel taking advantage of their capacity by laying the cache size smack down on amd instead of megahurtz.

    If it is cache size and not "look-ahead" then amd could (could mind you...but would they? and how many could they?) respond much quicker I'd think. If its new technology or a combo of cache and new tech then amd will be in a much worse position imho.

    Whatever the case its great for the consumer(me). Thank goodness for competition. Daddy needs a new pair of cores...and the price just got a whole lot better!

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

    It would indeed be very interesting to see a 2MB L2 1.6GHz Core 2 Duo E6200 compared against 2MB L2 1.6GHz Opteron 160.

    The shared L2 cache of the Conroe will give it a nice advantage though.
    Reply
  • bob661 - Tuesday, July 25, 2006 - link

    Anyonehave any speculation as to how much the initial Conroe's will cost? We pretty much know that the motherboards will be expensive but what about the CPU's? Reply
  • ChronoReverse - Tuesday, July 25, 2006 - link

    The pricing has been out for a while already. They're relatively reasonable considering the performance. Only the Extreme Edition as usual is really expensive (but still not as expensive as I'd have thought).


    Too bad the motherboards are so expensive. I'm taking a look at that Asrock board, but I doubt it'll have any good overclocking capability.
    Reply
  • Gary Key - Tuesday, July 25, 2006 - link

    quote:

    Too bad the motherboards are so expensive. I'm taking a look at that Asrock board, but I doubt it'll have any good overclocking capability.


    The less expensive boards for Conroe will fully hit the market near the end of August. ;-) We expect to see ECS, Foxconn, MSI, Epox, and others fully ramped up in a couple of weeks on the value boards. Until then, the Gigabyte DS3 is a really good board for overclocking the E6300/E6400 series and our Biostar and Abit boards continue to improve with each bios release. All three are under $145 now with others joining them shortly if the P965 is interesting to you. The ASRock board actually surprised us, but remember the VCore voltage cannot be adjusted. The $50~$100 market will be very interesting as the 945P, 946PL, and NV570SLI chipsets will dominate this section until the G965 boards start arriving in September if decent intergrated graphics are on your wish list, if not all of the boards will offer good performance for the money. The under $55 market will consist of VIA and SIS chipsets from PC-Chips and ASRock with a few majors like ECS and MSI having boards based on these chipsets.
    Reply
  • Wesley Fink - Tuesday, July 25, 2006 - link

    Everest Scores have been rerun with Version 3.01, which was released on July 16, 2006. Since the scores from the new version can not be compared to older Everest scores, we reran all the Everest benchmarks. 3.01 is said to provide full and complete support for Conroe and Merom. Values are different in that Memory WRITE and READ scores are reported as much higher than past Everest testing. Latency is also reported as closer between AM2 and Core 2 Duo with the 3.01 version of Everest. Charts and commentary have been revised using the new results. Reply
  • jjunos - Tuesday, July 25, 2006 - link

    Thanks for the update wes! It always shows the quality of the website when they listen to their community and and willing to rerun all their tests in the sake of being correct! kudos! Reply
  • TonyB - Tuesday, July 25, 2006 - link

    is it just me or did AMD just get pwned? Reply
  • bob661 - Tuesday, July 25, 2006 - link

    quote:

    is it just me or did AMD just get pwned?
    I personally don't care about who owns who. I just want competition so I can get this stuff for cheap. I'm a best bang for the buck guy.
    Reply
  • goinginstyle - Tuesday, July 25, 2006 - link

    Everyone benefits here with the performance improvements Intel has brought to the table and an AM2 3800+ at $150 is just an incredible value. Conroe made it easy for AMD users to upgrade their performance for very little money. Reply

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