DDR/NetBurst Memory Bandwidth and Latency

One of the most talked-about AMD advantages of the last couple of years has been their on-processor memory controller. This has allowed, according to popular theories, the Athlon64 to significantly outperform Intel NetBurst processors. The fact is NetBurst DDR2 bandwidth has recently been similar or wider in bandwidth than Athlon64 - even when the DDR is overclocked. You can see this clearly when we compare Buffered and Unbuffered Bandwidth of a NetBurst 3.46EE to an AMD 4800+ x2(2.4GHz, 2x1MB Cache) running DDR400 2-2-2 and running overclocked memory at DDR533 3-3-3.

The green bars represent DDR memory performance, while the beige to red are increasing DDR2 speed on NetBurst. Light green represents DDR400 2-2-2 while Dark Green is overclocked memory at the same CPU speed, DDR533 at 3-3-3.

Standard (Buffered) Memory Test


In buffered performance, Fast DDR400 is only faster than DDR2-400 and slower than DDR2-533, 667 and 800. Overclocked memory at DDR533 3-3-3 is faster than any of the DDR2 bandwidths on NetBurst.

The Sandra Unbuffered Memory Test, which turns off features that tend to artificially boost performance, is generally a better measure of how memory will behave comparatively in gaming. The same green for DDR applies here.

Unbuffered Memory Test


Without Buffering, DDR400 has the smallest bandwidth of tested memory speeds and timings. Even overclocking to DDR533 allows the DDR to barely beat DDR2-400. DDR2-533, 667, and 800 all have greater Unbuffered bandwidth than the DDR overclocked to 533. NetBurst DDR2 memory bandwidth is generally wider than the bandwidth supplied by DDR memory on Athlon64. Despite the wider bandwidth, the deep pipelines and other inefficiencies in the NetBurst design did not allow the NetBurst processors to outperform Athlon64. Keep this in mind later, when we look at AM2 and Core 2 Duo Memory Bandwidth.

Latency

The other area where AMD has had an advantage over NetBurst DDR2 performance is memory latency, the result of the on-processor memory controller. Comparison of the AMD DDR Memory controller and the Intel DDR2 Memory controller in the Intel chipset shows AMD DDR with latency about 35% lower than Intel NetBurst in Science Mark 2.0.

Memory Latency Comparison - DDR & NetBurst


While memory bandwidth was very similar between AMD and NetBurst, the deep pipes of the NetBurst design still behaved as if they were bandwidth starved. On the other hand the AMD architecture made use of the bandwidth available and the much lower latency to outperform NetBurst across the board.

Index AM2/Core 2 Duo Latency and Memory Bandwidth
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  • OcHungry - Wednesday, July 26, 2006 - link

    As far as expensive DDR2 is concerned, apparently you dont understand my logic.
    You dont need DDR2 800, 1000, and so forth for AMD.
    You can buy DDR2 667 which is cheaper and has better timings than DDR2 1000.
    With IMC in play, you can and should run FX62 @ 333mhz (FSB and mem speed) using 1:1 ratio. AMD gives us this option thru. IMC and we are not overclocking and being unfair to E6800, just increasing the mem/cpu link to what it should be. Althoug, Running FX @ 200 HTT/FSB compared to E6800 @ 266 would be unfair to AMD. If Intel could run @ 333mhz, so be it.
    My calculations are correct and were based on the benchmarks provided by the anandtech review (here).
    The only thing that need to change is the % gaine from memory timings (which was not mentioned first in the article). scratching off the memory % gain from my calculation, The new figure put FX62 at about 7% slower than E6800.
    But I am amazed how people are forgetting that we are comparing old architecture w/ the new and do not consider K8L or 4x4.
    4x4 is due shortly- Lets see if "the new king" willingly hands over the crown.
    Must have felt good crowning for less than a month (considering retail not available yet, and less than a month 4x4 is due).
    Reply
  • zsdersw - Wednesday, July 26, 2006 - link

    I'm amazed that you're expecting us to compare what's soon to be out with what's not-as-soon to be out (K8L, 4x4).

    If you're going to keep shifting the goal posts to suit your AMD fanboy desires, then you're never going to be happy with anything that doesn't tell you what you want to hear.
    Reply
  • Gary Key - Tuesday, July 25, 2006 - link

    quote:

    If we add all the mentioned optimal settings for FX62: (11%+3%+7%) = 21% increase in performance should have resulted- which is fair, accurate, and represent the true comparison of FX62 against E6800.


    The true comparison of the FX62 against the X6800 is 2.8GHz against 2.93GHz as they are shipped from AMD and Intel. That is the absolute base comparison and is about as fair, accurate, and truthful as it can get at this time. If you insist on optimizing (overclocking) the FX62 platform then you must realize it is equally fair to do this on the Core 2 Duo platform as well.

    quote:

    Most probably The timings used were: 4-4-4-12 (corsair DDR2 800). Tightening the timings to 3-3-3-8 would have given another 7% to 10% boost in FX62's performance.

    The timings used at DDR2-800 were 3-3-3-9. You will not see a 7% to 10% increase in performance.

    quote:

    As far as gaming is concern, we know vid card is the deciding facto. So I believe AMD has position itself perfectly for every corner of the market.To say Intel has captured the mid and high end of the market, is as erroneous as when Intel was pushing Netburst to capture gaming enthusiasts. We know that marchitecture and All that PR failed then, and will fail agin now.


    If the GPU is truly the deciding "facto" for gaming then your logic is up for debate. So, based upon your stated logic it should not matter what CPU is utilized, which equates to Netburst being equal to Athlon 64 in this performance sector. That means Intel was correct for marketing Netburst to the gaming enthusiats. We all know that is not true but are we to now believe it is based upon your statements? It sounds like a $42 Celeron D will perform equally to a $999 FX62 in gaming based upon your logic. I disagree of course but if it is okay to argue that Athlon 64 is a superior performing processor to the P4, then explain to us why is not okay to show Core 2 Duo being a superior processor to the Athlon 64 at this time.

    We are performance centric, the same conversations and excitement about a processor series occurred when the FX-51 was released and continued to occur for three years afterwards. Intel has finally countered with an excellent processor series and now it appears to be an issue to discuss peformance advantages without resorting to "My calculations show an overclocked CPU can beat a stock clocked CPU." If you know for a fact that at 9x330HTT and 3-3-3-8 1T settings the FX-62 will match or exceed the performance of a X6800, then please post the screenshots as I am sure all of us would be intrigued by this. However, also post the comparison of your X6800 running on stock voltages at 3.46GHz in order to reflect the true capability of the X6800 also.
    I look at it this way, everyone but AMD and Intel win this summer. I know a couple of AMD machines in the house are getting 3800+ X2 upgrades and my primary machine will be sporting a E6600. However, this price matching and slashing is going to have a long term effect on both companies and in the end that might not be healthy for this industry in a couple of years.

    quote:

    Further more, 64bit OS and window vista is reported to give AMD about 16% improvement compared to 10% for conroe. This will give another 6% boost in performance...


    Not seeing this difference in build number 5472 of Vista.
    Reply
  • OcHungry - Tuesday, July 25, 2006 - link

    I see, the moderators keep Editing the review article. the mem timings were not there when 1st read it. oh well Reply
  • goinginstyle - Tuesday, July 25, 2006 - link

    Dear OC-Sharikou,

    "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." As posted by Wes earlier and hopefully he will place these in the review shortly to shut you the hell up. Your calculations are already incorrect since you ASSumed the DDR2-800 memory was set at 4-4-4-12 and therefore your calculations of the FX62 being another 7 to 10 percent faster are WRONG. Do you understand yet that calculating instead of testing means you are going to be WRONG. You consistently make false and misleading statements here and elsewhere on the internet. We now understand why Intel fired your lazy calculating ass. You were probably the one who devised their P4 marketing scheme to compete against the Athlon 64. I bet all of your calculations at the time proved higher core speeds and memory bandwidth resulted in higher scores against the AMD processors. It was obvious that calculation was WRONG.

    Let's see some benchmarks on your FX62 instead of some asswipe musings about percentage based benchmarking. Answer this simple question, why is AMD shipping their CPUs at a 200HTT base? How do you honestly expect to compare a highly HTT overclocked FX62 against a stock Conroe? If their 2.93 Conroe runs at 3.5GHz on stock voltages then would it not be fair to test the Conroe at this speed and the FX62 at your holy 9x330 setting? By the way, in real application land, 1T over 2T might mean a 1% difference at DDR2800, try it yourself. Oh yeah, I f@$&ing forgot you do not own a FX62 or Conroe so you have to use pencil and paper to make your wet dreams come true.
    Reply
  • drarant - Tuesday, July 25, 2006 - link

    Think of it this way, X6800 will perform about 10-20% higher than a FX-62 whether its a set of DDR2-667 or DDR2-1067, roughly $150 ram vs $250 ram. Whereas, in your proposal, You would need RAM to run at 330 x 4 = DDR2-1320... even if it does exist in the next 6months, it will have to be run @ 2T and 4-4-4 at the tightest.

    So even though almost all of your speculation is wrong (i.e. 4-4-4 > 3-3-3 does NOT give a 7-10% boost) and the rest is assumption (i.e. 4-4-4 2T is what was used) you still cannot do what you propose to reach a Stock Intel CPU. (Get over it, I did)
    Reply
  • zsdersw - Tuesday, July 25, 2006 - link

    Pretty much everything you've said is erroneous. Reply
  • zsdersw - Tuesday, July 25, 2006 - link

    That was for OcHungry, not Wesley Fink. Reply
  • Wesley Fink - Tuesday, July 25, 2006 - link

    When AMD was the performance leader I was called an AMD fanboi, now when Core 2 Duo is top performer I am called an Intel fanboi. That means things are balanced as they should be. Does it ever occur to some that we are fans of PERFORMANCE - carefully compared and measured performance. We did a more than fair comparison overclocking AM2 to the same speed as Conroe and increasing clock speed to 266 to run an unsupported DDR2-1067 - which should favor AM2 as it appears to improve more with memroy bandwidth than Conroe. AM2 still lost by a wide margin.

    I could even understand your argument if you compared a 4GHz Core 2 Duo, which I am personally running on air, to the highest overclocked AM2 - or even AM2 to Core 2 Duo at the same overclocks and "bus" speeds. I am left to conclude that you surely know more than AMD since they have reduced prices in-line with performance credible review sites have found on AM2 and Core 2 Duo. If AMD believed yours was a realistic comparison the prices would never have been reduced.

    An apples-to-apples comparison is not a mystery. Comparing a super-overclocked and bus increased AM2 to a STOCK Core 2 Duo is fanboi.
    Reply
  • duploxxx - Wednesday, July 26, 2006 - link

    I understand that there are several comments of fanboy'ism that might not be correct, but from the moment you guys went to the click the button visit the comments/conclusions/headers just became no longer "balanced" for example "a new king has born"... the woodcrest isn't that better then the current opteron sure it will have the highest clock cpu and best performance on that 3.0 (when we even can buy it) but compare apples with apples and put a 2,6 versus a 2,66. and making such a statement knowing that the competitor comes with a new revision just a month after.... (not sure if you posted the review btw... its just global anand) same with conroe, it has the performance crown. like amd had it for 3years. never saw a statement when a new fx arrived like "The empire is kicked again". now just new performance blabla. Reply

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