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.
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poohbear - Wednesday, April 12, 2006 - link
>> It's 2006 and there are still tons of people using athlon xps and agp, so plz drop your enthusiast perspective on the market, it's not realistic of what the avg person has.>>>>Huh!? And what does this drivel has to do with whether AM2 or S939 is the best choice for a new computer build in the next few months?
what im saying w/ that "drivel", is that ppl are gonna have their s939 for a long time to come, the fact that lots of avg folks still use athlon xps and have agp, is proof of the previous gen staying around a whole lot longer than the manufacturers would care for. you call it "drivel", i call it proof. whatever, it's just another internet argument.
yes, if u're buying a new system, and u're an avg user, then a s939 will suit your needs fine for the next 2-3 years. If the AM2 is the same price as the s939 when it's released, then ofcourse the choice is obvious, aside from it being a new port and the s939 being a mature and stable port. about the EOL stuff, the Athlon xp has been EOL for a long time, but we can all find those chips easily for dirt cheap, EOL doesnt mean jack all if u know where to find them. thank u, and here's to another 2 years on my s939 rig.:)
Brunnis - Tuesday, April 11, 2006 - link
>> nope it makes perfect sense. i wouldnt hold my breath for the am2 is what im saying.No, you made it seem like Anand recommended AM2 for people that already own reasonably fast S939 systems. The fact is that Anand did the exact opposite. What Anand said is that there's no point in buyin a S939 system for those who have older computers, which makes perfect sense. Don't you agree?
>> im sorry but a 5% increase doesnt justify ditching my s939 and opty 144.
Yeah? And who told you that you should? It wasn't me and it certainly wasn't Anand. I was talking about people with older systems, as was Anand, yet you fail to comprehend what either of us wrote. Way to go.
>> and what are u talking about limited life? w/ dualcores available on the s939 they're gonna be around well into 2008.
So, if I were in the market for a new system you'd recommend me to buy a complete S939 system insted of AM2? AM2 will likely get 65nm K8L CPUs and possibly quad cores. I'm sure S939 is great and all, but it probably won't have much faster CPUs released for it and it's therefore pretty dead. Notice that I'm still not recommending S939 owners to switch on the launch of AM2, or that current 939 systems will be slow compared to the initial AM2 systems.
>> It's 2006 and there are still tons of people using athlon xps and agp, so plz drop your enthusiast perspective on the market, it's not realistic of what the avg person has.
Huh!? And what does this drivel has to do with whether AM2 or S939 is the best choice for a new computer build in the next few months?
Gnarr - Monday, April 10, 2006 - link
Since we only see a 35% percentage increese in bandwith with AM2, we should see the same gains from DDR2-533 as DDR2-800.DDR2-533 in dualchannel offers 8528MBps, but 6800MBps seems to be the peak bandwith for AM2 as is.
Furen - Monday, April 10, 2006 - link
Yes, DDR2 533 and DDR2 667 benchmarks would have been useful, considering that these are the cheaper types of DDR2. Just because the max bandwidth for DDR2 533 is still higher than AMD's current bandwidth it doesn't mean that it'll achieve the same usable bandwidth unless AMD is currently being bottlenecked by a data link rather than by the mem controller's efficiency.highlandsun - Monday, April 10, 2006 - link
Eh... With the arrival of DDR3 looming for 2007 it makes no sense to me to build a DDR2-based system now. DDR is still about the same price as DDR2, and where DDR2-800 gets a tiny performance edge over DDR-400, that edge completely disappears with DDR-500, or even a mild degree of overclocking.Or at least, performance isn't sufficient motivation to switch, and price doesn't seem to be either. Perhaps power efficiency, since DDR2 is lower voltage.
Calin - Monday, April 10, 2006 - link
If we assume you are talking about an AMD system, then DDR3 won't be a possibility until maybe three years from now. They just moved out of the Socket 939, and into a new socket. Next socket you will see will be in more than a couple of years...Yes, performance and price are not reason to switch now. Power efficiency for sure, if you will buy a low power processor (from 89W TDP to a 35W TDP, that is some 50W of power in best case, and possibly 25W in the worst case).
What other reason to switch could you have? Access to more memory (maybe), I don't know how much memory those new processors could access (more than 4GB? current mainboards seem limited to 3GB). Availability of high performance memory - fast DDR memory will dry up sooner than later. Processors will dry up too.
JarredWalton - Monday, April 10, 2006 - link
Can you point to any DDR3 chipsets for CPUs on the horizon? Intel is sticking with DDR2 for now, and DDR3 is basically only being used in GPUs. It could be several years before we see DDR3 chipsets on motherboards - assuming we don't just skip that option altogether and go some other route.NullSubroutine - Monday, April 10, 2006 - link
ddr3 and gddr3 arent the same things.menting - Monday, April 10, 2006 - link
right now DDR3 is still slated to sample in mid 2007, and announced late 2007 / early 2008 timeframe.DrMrLordX - Monday, April 10, 2006 - link
Word is AM3 will be out by 2007, giving AM2 a product life of maybe one year, maybe less.http://forums.anandtech.com/messageview.cfm?catid=...">http://forums.anandtech.com/messageview.cfm?catid=...
Of course, this is nothing but rumor and speculation, but it's a common rumor. If this is even remotely true, AM2 is nothing but a stopgap measure.