Final Words

If AMD's Socket-AM2 only offers a minimal performance increase, then why on Earth is AMD moving to it?

AMD has done a tremendous job of making DDR-400 last with their architecture. When Intel first talked about moving to DDR2 there was concern that AMD's delayed move to the new memory technology would result in it being behind the curve, but the absolute opposite held true; Intel showed no benefit from DDR2 initially and AMD did just fine with only DDR-400.

However times are changing, and after a very long hiatus Intel will soon resume increases in FSB frequency, not to mention that their new Core architecture is considerably more data hungry than anything we've seen to date. So on the Intel side of the fence, the greater bandwidth offered by DDR2 will finally have a real use. With Intel DDR2 demand increasing and more manufacturing shifting away from DDR, it now makes sense for AMD to jump on the DDR2 bandwagon as well. If AMD does it early enough, the transition to DDR2 will be complete before any of its products desperately need it, which is always a better route.

It's not the most convincing reason to switch to DDR2 today, but AMD has stayed on DDR1 far longer than anyone expected and it's better to be early than never. The fact of the matter is that CPUs will get more cores, reach higher clock speeds and feature more data-hungry architectural changes, all of which require more memory bandwidth. AMD's options are to either add more memory bus pins to the already staggering 939-pin package, or to embrace a higher bandwidth (and lower voltage) memory standard; the option it chose makes a lot of sense.

There's also this issue of efficiency; based on our ScienceMark results, AMD was able to build an extremely efficient DDR-400 memory controller into their processors. The Rev E processors are able to deliver over 5GB/s of memory bandwidth, which is extremely close to the 6.4GB/s theoretical maximum offered by a 128-bit DDR-400 memory interface. The Rev F AM2 processors we've tested aren't able to break 7GB/s yet, which albeit an increase of 35% over the best Socket-939 numbers we've seen, still ends up being only 53% of the peak bandwidth offered by a 128-bit DDR2-800 memory controller compared to the almost 80% we saw on the Rev E.

If we use history as our predictor of the future, it may take a few more revisions of AM2 before we see that sort of efficiency, if we ever do. AMD has come a very long way since the performance we saw back in January, and if that's any indication we may just end up seeing better performance out of Rev G and H processors in the future. The verdict is also not out on Rev F; although the launch is only two months away, we keep on hearing that availability won't be until July. While that's not enough time for AMD to be making major changes to the silicon, it is quite possible that the changes have already been made and they're just waiting to get new chips back from the fab.

Based on what we saw with the Rev E cores and DDR-500, coupled with our results here with DDR2-800, it looks like Socket-AM2 will offer minor performance gains across the board if paired with very low latency DDR2-800, but otherwise it looks like it'll offer performance as good as Socket-939. If you're looking for numbers, with DDR2-800 at 3-3-3 we'd expect to see 2 - 7% gains across the board, with the 7% figure being reserved for applications like Quake 4 or DivX and the 2% figure being far more common.

Why would you move to Socket-AM2? If you're well invested in an up-to-date Socket-939 system, and if these numbers we've seen here today hold true for shipping AM2 platforms, then there's no reason to upgrade immediately. However, if you're buying or building a brand new system, then by all means AM2 makes a lot more sense than Socket-939. Like it or not, DDR2 is the future, and AM2 will be the new socket for AMD's future 65nm parts as well. DDR2 is also competitively priced with DDR memory while generally offering higher bandwidths, and with most manufacturers transitioning to DDR2 now we expect to see further DDR2 price cuts.

With AM2 you are investing in memory that will have a longer lifespan and a motherboard that will have a better upgrade path than Socket-939 today. The only other advantage other than a more secure upgrade path that AM2 offers is AMD's upcoming Energy Efficient desktop CPUs. We're particularly intrigued by the 35W Athlon 64 X2 3800+; if you thought AMD's processors were cool and quiet, a 35W X2 should blow you away. (It might overclock really nicely as well!)

The disheartening news for AMD and its fans alike is that if AM2 can't offer significant performance increases over what we have now, then all Intel has to do is execute Conroe on schedule, delivering the performance we've been promised and 2006 will be painted blue. AMD has been telling us that 2007 is the year we'll see major architectural changes to their processors, so AM2 may very well be as good as it gets for now. That's still very good, of course - the fastest X2 chips still outperform the fastest Pentium D chips - but it looks like after three years K8 may finally get some competition for the performance crown.

Does AM2's Performance Make Sense?
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  • Thor33 - Monday, April 10, 2006 - link

    It seems the test was done with the fastest memory available in fact is a PC2-8000 1000mhz rated. OCZ EL DDR2 PC2-8000 / 1000 MHz / Platinum XTC / Extreme Edition
    http://www.anandtech.com/memory/showdoc.aspx?i=273...">http://www.anandtech.com/memory/showdoc.aspx?i=273...
    Unless there is a typo on the test memory utilized below is PC8000 drop down to work as PC2-6400?
    Memory:
    PC2-6400 OCZ PC8000 DDR2-800 4-5-4-15 (1GB x 2)
    OCZ DDR-400 2-3-2 (1GB x 2)

    The test should be a PC2-6400 which is DDR2-800 mhz rated memory. If this test is performed with an average memory maker DDR2 PC2-6400 memory the score will be even less impressive. This is worth mentioning.

    Rated at DDR2-1000, this OCZ announces right off the bat that it is serious new memory. Past DDR2 has struggled to reach DDR2-1000, so rating this new OCZ at DDR2-1000 is a "look-at-me" announcement. The rated timings of 4-5-4-15 at DDR2-1000 are also exceptionally fast for DDR2 memory at that speed. By the way, for those of you who have trouble translating PC speed ratings to Memory Speeds, all you have to do is divide by 8. Thus PC2-8000 is DDR2-1000 speed, PC-5400 is DDR2-667 (results are approximate), PC2-6400 is DDR2-800, etc.

    Reply
  • waldo - Monday, April 10, 2006 - link

    I haven't heard anything about changes in regards to the opteron platform, or are they staying the same. I would assume they would change to use the ddr2 memory as well.

    I actually can't see how purchasing a new AM2 system is good for anyone, whether a new system or upgrading. With prices being higher, almost double, and parts being barely similar in performance with premium boards, memory, etc., it doesn't seem like a good idea for anyone to hop on early to the AM2 platform. Just seems like a waste of a lot of money. In this case, the latest is not the greatest.
    Reply
  • bob661 - Monday, April 10, 2006 - link

    Where are the double prices? The ram is more money but everything else looks to be the same. According to http://tinyurl.com/koapt">this, the prices for the CPU's are the same as current one's. I doubt the motherboards will cost more than the typical new release prices. Reply
  • petz - Monday, April 10, 2006 - link

    What was the date code on the CPU? Why no screenshot showing that the CPU was at least recognized? The BIOS memory settings are meaningless if the CPU is not properly recognized. I would have done a disk benchmark, because the fact that the poorest result was from Business Winstone tells me that something was wrong in that department. Reply
  • Anand Lal Shimpi - Monday, April 10, 2006 - link

    The shots of the chip itself were kept out of the review to protect our source for the chips obviously. A difference of 0.1 points in Business Winstone is within the normal margin of error (< 3%) for that benchmark, the difference itself is basically 0. The CPU was also recognized properly by the BIOS.

    Take care,
    Anand
    Reply
  • nicolasb - Monday, April 10, 2006 - link

    It seems to me that socket AM2 is likely to be just a stepping stone. Current AMD processors don't need DDR2 - but the next generation will.

    Conroe seems likely to stamp all over AMD for a few months. The point when things will get interesting again is when we see quad-core processors begin to ship from both Intel and AMD.

    AMD's architecture has been tuned for multi-processor systems right from the start. Post-Conroe quad-core chips may be a bit clunky - effectively two dual-core chips glued together, in the same kind of way that Pentium D is two single-core chips glued together. AMD may therefore regain the lead in the quad-core arena - if there are no other limiting factors, such as memory bandwidth.

    If a dual-core chip is using barely half of the available memory bandwidth of DDR2-800, what that means is that a quad core chip will not be significantly limited by memory bandwidth. I think this is what AMD is planning: they will need DDR2 bandwidth for quad-core, and they want to switch over to it now to get all the bugs ironed out in time for K8L. So socket AM2 has no significance for the current generation of chips, and was never meant to have: it's merely preparation for 2007.

    If this is true, then the fact that current chips use only half the available bandwidth may actually be deliberate, and something that won't change.
    Reply
  • sprockkets - Monday, April 10, 2006 - link

    I like your post.

    Remember the KT266 fiasco? Then KT266A, then KT333, then KT400?

    Yeah, the KT266A killed everything, when the KT266 showed no performance gains and just like then, said memory bandwidth is useless for AMD Athlons.

    Except the problem here is, to get an updated "chipset" or memory controller, you have to upgrade the processor and perhaps the board, and AMD has already done 3 rev of the processor.
    Reply
  • MrKaz - Monday, April 10, 2006 - link

    PC133 SDRAM > DDR at early stage
    PC133 SDRAM > RDRAM at early stage

    It will improve on next revision I bet, I was expecting 0% improve.
    This is just a RAM type exchange.

    You AMD systems users must show appreciation to AMD for the excellent platform they developed.

    With Intel each time there is a memory speed bump, you "have" to upgrade the motherboard because of the memory controller on the chipset, even if Intel decides to keep the same socket. How many times since DDR266 have Intel “forced” people to upgrade motherboard/chipset in order to catch up every time there is a memory speed bump?

    Even at the same RAM speed Intel “offers” (example) 865 and 875 chipsets where one is faster than the other with the same RAM?

    Since AMD integrates the memory controller, you never get problems like that. AMD integrated memory controller is compatible with DDR 266 to 400 (unofficial 433,466,500).
    With DDR2, you will get 533,667,800 (unofficial 933, 1066).
    You always keep the same board and RAM. The processor is the only that changes.
    If AMD didn’t get socket 754, and only 940 or 939 we where looking at the perfect computer platform.
    Reply
  • Calin - Monday, April 10, 2006 - link

    RDRAM was a very bad choice for the processors to which was first mated. Pentium !!!, like the Athlons of today, fare better on low latency lower bandwidth memory than on high latency high bandwidth memory (as RDRAM was). However, RDRAM has its place in small devices - where you can not fit all of the 168 pins of SDR memory, or all of the 180+ of the DDR memory.
    Pentium 4 was doing very well on RDRAM, dual RDRAM was quite a bit faster than dual SDR or single DDR. There was a time when intel 850 with dual RDRAM was the high mark in the chipsets
    Reply
  • flyck - Monday, April 10, 2006 - link

    RDRam had a LOWER latency then DDR.

    Mainly because of the superior chipset design (which had less internal latency).
    Reply

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