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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  • sprockkets - Monday, April 10, 2006 - link

    No one thought that making a more capable ILP was possible, but intel proved that wrong. They all thought ILP was dead due to the P4, which is ironic.

    Would I wait for AM2? Why? Crucial Ballistix Ram in DDR-400 is $95 for 512x2, whereas DDR800 is $185.

    NO. Little to nothing is not worth $90 in memory plus a premium in boards and processor prices.
    Reply
  • sprockkets - Monday, April 10, 2006 - link

    I mean ddr2-800 Reply
  • flemlion - Monday, April 10, 2006 - link

    This seems to be just a quicky review. In the conclusion it is mentioned that the usefullness of memory bandwith increases as the CPU clock speed increases. But still a lower speed was used for this test than for the DDR1-400 versus DDR1-500 evaluation. It seems to me at least this test should either have been done at different speeds to get a feel of this impact or at minimum at the same speed of the DDR1-400 versus DDR1-500 article.
    As a sidenote, it's also interesting to see that the test config has no mention of the CPU speed that was used. If this is NDA, then say so, if not it just appears as hiding the details that would expose this article as gossip instead of information.
    Reply
  • andrewln - Monday, April 10, 2006 - link

    I meant...
    Intel will see how the next generation of AMD works just 5% faster....wouldn't they tune down conroe to match or make it just a bit faster than AMD and sell at the premium price? Since the demand will be almost the same.
    1) AMD fanboi will keep on buying AMD
    2) Intel fanboy will keep on buying Intel
    3) But this time, people that wants performance, will be buying Intel (even though its only a 10% faster than the competitor, or 40$)

    This way, when AMD makes a new gen of procesor, Intel only have to tune up Conroe which is cheaper than making another big modification that might or might not work.
    Reply
  • Conroe - Monday, April 10, 2006 - link

    They said 20%, and thats where they plan on staying. Theu could have more. The FX-62 has extra cache, it may give 10% who knows? Reply
  • Anand Lal Shimpi - Monday, April 10, 2006 - link

    Every FX-62 I've seen hasn't had any more cache than what's in the table in the review.

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

    I’ve got to disagree- I don’t think this makes sense to even upgrade from a 754 system to AM2.

    Why? Because if you remember Nforce 2- and all the Mb’s with “future- proof” DDR-400 systems, the MB makers did not live up to their claims. For most recognized mfg’s it took the revision after DDR-400 memory was available before most of them got it right.

    So I don’t see where AM2 can even be thought of as an upgrade path, especially before final revisions have been made in silicon. A MB you buy initially might work, but with future memory or processors… forget it. Anybody wanna take a bet ($1 will get you $10), that the first MB’s out by lets say- ASUS, do not allow for different memory timings or the latest memory say March of 07?, let alone a top of the line processor, same date?

    While the author did say many changes are still in the works, final silicon may not yet even been achieved. How can buying a MB now be considered a possible upgrade in the future?

    For this reason, and many price/performance reasons, I have a 754 system, and I will hope that after tax season ends I can build a 939 for a better price. That’s it.

    The numbers per the review state this clearly. This is not about performance. And it will be expensive. The analysis on the forum here site seems to indicate that the relative analysis is expected future performance, when Anand admittedly and AMD (by not making announcements about performance) seem to indicate (and I explicitly do) that this is not about performance…. Yet either. So how can this even be recommended as an upgrade path when there is very little real world benefit and future compatibility a MB purchased now and memory or processors is not even known.

    I am an avid fan of AMD, but I think excess hype can kill a product as quickly as bad rumors.
    Reply
  • HammerFan - Monday, April 10, 2006 - link

    I'm suprised that nobody has considered the bottlenecks in AMD's systems as of late. Recently, it seems that all AMD really needs to do with the K8 is keep squeezing more MHz out of it. Clearly the CPU has enough memory bandwidth to spare, so bring the rest of the processor up to speed. IIRC, AMD is starting to implement an improved version of SOI in their new CPU cores (or is it 65nm cores?), which will help increase clock-speed headroom. Also, as quality continues to improve, AMD might be able to add higher clock speeds to take advantage.

    just my $.02

    HF
    Reply
  • ozzimark - Monday, April 10, 2006 - link

    one thing that would REALLY help K8... follow intel's footsteps with netburst and try to double-pump the ALU. faster SSE execution never hurts either :) Reply
  • still - Monday, April 10, 2006 - link

    Double-pumping the ALU is only going to limit scaling and increase heat... what the K8 core really needs is better L1 and L2 cache subsystem.... The L1 is sort of ok but getting old it the same one the K7 (7 year old). They improved the L2 of the K8 over K7 but half heartedly. It still has too narrow of a path and too high of a latency. I can just imagine what the K8 can do with a 4M low latency cache that has 256 or 512 bit width data path (+ ECC of course).
    While they are there lower the L1 latency to 2 cycles. That alone is 5-10 % improvement.
    And they need to seriously improve the SIMD execution units. The current AMD SIMD units are almost as lame as the Intel implementation of AMDs 64bit instructions.
    Oh yeaa and write some decent compilers to make use of the 64 bit goodness like extra register - where are the promised 20 % improvements?
    The K8 core can scale better than Conroe and can crunch trough more instructions/data if the cache subsystem can feed all these to the execution units. Albeit the K8 has to be clocked slightly higher to do that - such is the tradeoff of 3 vs. 4 IPC.
    Reply

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