First Look: AM2 DDR2 vs. 939 DDR Performance
by Wesley Fink on April 17, 2006 12:05 AM EST- Posted in
- CPUs
Final Words
When the article OCZ EL PC2-8000 XTC: Low Latency PLUS DDR2-1100 was posted a couple of weeks ago, the potential of this incredibly fast DDR2 memory on the upcoming AM2 platform was clear. What was not expected was that the opportunity to run the DDR2-1000 memory through its paces on an AM2 was only a couple of weeks away. After looking more closely at DDR2 memory performance on the 4th spin of the AM2 processor it is clear AMD will definitely be able to launch AM2 with the expectation of better performance than the Socket 939 it replaces. This avoids one of the huge pratfalls that plagued Intel in their move to DDR2.
However, the memory bandwidth increases of up to 30% on AM2 and the Latency improvements of 12 to 16% compared to the fastest DDR memory on socket 939 do not yield much in real-world performance. The real-world performance increase for AM2 compared to Socket 939 will likely be very small - in the range of no increase to about 7%, depending on the application.
In normal times this would be great news! In times where previews of Intel's new Conroe architecture show solid 20%+ improvements in performance compared to AMD Socket 939, these smaller AM2 increases are reason for concern. It certainly appears that unless some unforeseen miracle happens, the move from Socket 939 DDR to AM2 DDR2 just can't generate anywhere near the performance improvement AMD really needs to combat Intel's Conroe. This article evaluated memory and gaming performance, but you can see comparisons of General Performance, multimedia and encoding in the companion article AMD Socket-AM2 Performance Preview.
Not all is gloom in the AMD camp, however, as there are certainly bright spots. AM2 IS faster than Socket 939, with even more possible DDR2 bandwidth for the future. Unfortunately, unless AMD makes revisions to the core and/or adds more cache with the 65nm die-shrink there is not much improvement from the move to AM2. The extra bandwidth and lower latency just don't translate into meaningful performance improvements with today's applications.
There are also a few general observations about using DDR2 with the new upcoming AM2. Using fast, top-line memory DDR2-533 is roughly equivalent in bandwidth to fast DDR400 memory. That observation should also hold with mainstream memory where DDR400 3-3-3 should perform about like DDR2-533 4-4-4. Most memory manufacturers will also be producing fast high-end DDR2-800 and more mainstream DDR2-667 and DDR2-800 parts for launch with AM2, so there will likely be many more memory choices when AM2 launches.
Last, the move to a unified memory specification with Intel will likely be a good development for those looking to buy new DDR2 memory. With AMD and Intel both using DDR2 there will likely be more innovation in the DDR2 market, more choices, and even better prices. Add to that the expectation that both AM2 and Conroe will launch with official DDR2-800 support and faster DDR2 memory should be much easier to find and afford in the near future.
It appears AMD will succeed in launching a faster on-processor DDR2 memory controller. The latest AM2 pre-release samples are showing significant improvements over Socket 939 DDR in both memory bandwidth and latency. Unfortunately, the current AMD architecture running current applications and games doesn't appear to need the additional bandwidth or reduced latency. This may change in the future, but for now the move to AM2 and DDR2 memory looks like it will yield far too little in performance improvements to keep AMD competitive in the upcoming desktop marketplace.
When the article OCZ EL PC2-8000 XTC: Low Latency PLUS DDR2-1100 was posted a couple of weeks ago, the potential of this incredibly fast DDR2 memory on the upcoming AM2 platform was clear. What was not expected was that the opportunity to run the DDR2-1000 memory through its paces on an AM2 was only a couple of weeks away. After looking more closely at DDR2 memory performance on the 4th spin of the AM2 processor it is clear AMD will definitely be able to launch AM2 with the expectation of better performance than the Socket 939 it replaces. This avoids one of the huge pratfalls that plagued Intel in their move to DDR2.
However, the memory bandwidth increases of up to 30% on AM2 and the Latency improvements of 12 to 16% compared to the fastest DDR memory on socket 939 do not yield much in real-world performance. The real-world performance increase for AM2 compared to Socket 939 will likely be very small - in the range of no increase to about 7%, depending on the application.
In normal times this would be great news! In times where previews of Intel's new Conroe architecture show solid 20%+ improvements in performance compared to AMD Socket 939, these smaller AM2 increases are reason for concern. It certainly appears that unless some unforeseen miracle happens, the move from Socket 939 DDR to AM2 DDR2 just can't generate anywhere near the performance improvement AMD really needs to combat Intel's Conroe. This article evaluated memory and gaming performance, but you can see comparisons of General Performance, multimedia and encoding in the companion article AMD Socket-AM2 Performance Preview.
Not all is gloom in the AMD camp, however, as there are certainly bright spots. AM2 IS faster than Socket 939, with even more possible DDR2 bandwidth for the future. Unfortunately, unless AMD makes revisions to the core and/or adds more cache with the 65nm die-shrink there is not much improvement from the move to AM2. The extra bandwidth and lower latency just don't translate into meaningful performance improvements with today's applications.
There are also a few general observations about using DDR2 with the new upcoming AM2. Using fast, top-line memory DDR2-533 is roughly equivalent in bandwidth to fast DDR400 memory. That observation should also hold with mainstream memory where DDR400 3-3-3 should perform about like DDR2-533 4-4-4. Most memory manufacturers will also be producing fast high-end DDR2-800 and more mainstream DDR2-667 and DDR2-800 parts for launch with AM2, so there will likely be many more memory choices when AM2 launches.
Last, the move to a unified memory specification with Intel will likely be a good development for those looking to buy new DDR2 memory. With AMD and Intel both using DDR2 there will likely be more innovation in the DDR2 market, more choices, and even better prices. Add to that the expectation that both AM2 and Conroe will launch with official DDR2-800 support and faster DDR2 memory should be much easier to find and afford in the near future.
It appears AMD will succeed in launching a faster on-processor DDR2 memory controller. The latest AM2 pre-release samples are showing significant improvements over Socket 939 DDR in both memory bandwidth and latency. Unfortunately, the current AMD architecture running current applications and games doesn't appear to need the additional bandwidth or reduced latency. This may change in the future, but for now the move to AM2 and DDR2 memory looks like it will yield far too little in performance improvements to keep AMD competitive in the upcoming desktop marketplace.
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Ecmaster76 - Saturday, April 15, 2006 - link
Wouldn't it be the best way to suck up bandwidth? We already knew a single core had enough bandwidth from the 754-939 transition.I guess its not that big a deal now because the parts aren't even for sale. But as long as you do tsome multitasking articles on the final hardware I'll be happy.
IntelUser2000 - Saturday, April 15, 2006 - link
So... the conclusion is that DDR2-800 is needed to outperform DDR400. DDR2-667 is slower than DDR400. The Inquirer is correct, contrary to some other opinions.Wesley Fink - Saturday, April 15, 2006 - link
Latency and Bandwidth of DDR2-533 are about the same as DDR400, and DDR2-667 and DDR2-800 are both faster. Games and Applications SHOULD be faster on both DDR2-667 and DDR2-800. However, given current aopplications and the AM2 memory controller, the applications and games are about the same at DDR2-667 - and DDR2-800 is faster as you state.This is likely the result of the late pre-release AM2 memory controller and applications/games themselves not being optimized for DDR2 on AM2. Both will likely be fixed very quickly, and actual performance of DDR2-533 should then be roughly on par with DDR400 - with 667 and 800 both faster.
psychobriggsy - Saturday, April 15, 2006 - link
If 2.5GHz was a 40% overclock, then the AM2 processor tested must have been running at 1.8GHz (9x200, i.e., it was also unlocked for you to get 10x250).It's not surprising that a 1.8GHz K8 processor wouldn't benefit from DDR2 much - indeed I expect that most of the application improvements were just from the slightly reduced latency at DDR2-800 rather than actually having more bandwidth available.
I wonder what a stock 2.8GHz AM2 X2 with DDR2-800 would get against a stock 2.8GHz 939 X2 with DDR-400? No, I don't think it will be a miracle, but just possibly it will start actually needing the extra bandwidth available, which could lead to a greater gap between the two platforms.
I guess we'll find out in under 2 months.
Wesley Fink - Saturday, April 15, 2006 - link
The AM2 processor was NOT a 1.8GHz x2. I stated the CPU could overclock 40% at stock speeds, but the 10x250 is not that 40% overclcok. We chose that ratio because it is a clock speed our DDR2 memory could handle and it was also a speed doable on 939 for a reasonable comparison. We actually had two AM2 processors this round, a top-line AM2 and a more mainstream processor. We looked at performance from both, and it was the same at the same processor speed. The DDR2 memory controller reports as Rev. F.As for the question about manufacture date, we are providing as little information about these pre-release processors and motherboards as possible to protect our sources. We have several sources who work with us to bring you the latest news before anyone else, and we don't want to compromise those relationships. Therefore we are not providing any information that might make it easier for AMD and others to trace our sources.
We can assure you these are the latest Rev. AM2 shipped to AMD partners in early April as we have evaluated 4 versions since mid-January. This is also the first rev. to fully support DDR2-800.
Viditor - Saturday, April 15, 2006 - link
Fair enough...had to ask.
Viditor - Saturday, April 15, 2006 - link
My concern is that while Anand is just receiving the part, if it's off of a recent production run then AMD will have some problems with the launch. Usually you need a full turn's worth of product in inventory for a launch...if they are just turning out final product now, then my guess is there will be shortages come July. Of course since they have doubled their capacity recently it will be much less, but still...it doesn't bode well.Anand, could you confirm the manufacture date of the chip you tested for us please?
Viditor - Saturday, April 15, 2006 - link
Apologies...I should have addressed the previous question to Wesley (sorry mate).I know that APM allows AMD to change anything (even down to individual dice on the wafer) at any point in the process, but my concern is inventory levels here. If you could please confirm the production date on the chip you used for testing, it would help me significantly with my analysis of the upcoming launch.
Cheers!
Jynx980 - Saturday, April 15, 2006 - link
Typo on page 3, paragraph 5:Wesley Fink - Saturday, April 15, 2006 - link
The extra "we" has been removed.