The Test
Unfortunately the platform that we were testing on would only allow us to run our DDR2-800 at 4-5-4 timings, instead of the 3-3-3 that's possible with this memory on socket 775. That hurts performance a bit, but the real world difference between 4-5-4 and 3-3-3 isn't going to be more than a few percentage points.
The only DDR2-800 we had on hand was in the form of 1GB modules, so we had to use a pair of 1GB DDR-400 which ran at 2-3-2, instead of the 2-2-2 we normally run with our smaller 512MB modules. Once again, the difference in performance isn't tremendous, but we wanted to explain why the timings were different than what we've used in the past.
Both our Socket-AM2 and Socket-939 Athlon 64 X2 processors ran at the same clock speed with the same cache sizes, so the results should give us a clear indication of whether or not AM2 is faster than equivalent 939 configuration.
| CPU: | AMD Athlon 64 X2 Socket-AM2 AMD Athlon 64 X2 Socket-939 |
| Motherboard: | ASUS A8N32-SLI (Socket-939) Unnamed MCP55 Socket-AM2 Motherboard |
| Chipset: | NVIDIA nForce4 SLI x16 NVIDIA MCP55 |
| Chipset Drivers: | nForce4 6.70 |
| Hard Disk: | Seagate 7200.9 300GB SATA |
| Memory: | OCZ PC8000 DDR2-800 4-5-4-15 (1GB x 2) OCZ DDR-400 2-3-2 (1GB x 2) |
| Video Card: | NVIDIA GeForce 7800 GTX |
| Video Drivers: | NVIDIA ForceWare 84.21 |
| Desktop Resolution: | 1280 x 1024 - 32-bit @ 60Hz |
| OS: | Windows XP Professional SP2 |
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savantu - Monday, April 10, 2006 - link
Anand , please correct the values in the table at the Adobe and multitasking tests , they should be negative.savantu - Monday, April 10, 2006 - link
..It's time so less is better.Anemone - Monday, April 10, 2006 - link
Don't forget capacity. If you loaded up 4 memory slots to bring 939 machines to 4gb, you harmed timings. DDR2 can bring 2gb on a module at good timings and thus make a higher performance 4gb machine. Why is this important? In Vista (yep I know it's delayed) you will find that gamers and power users of a wide variety will want 4gb machines, much the same as a good number of folks are starting to use 2gb machines now. The larger footprint of Vista ups the ante. It's not that 2gb won't be enough, it will do. Just as 1gb today "will do". But come the end of this year 4gb will start to be that cutting edge amount and that suits the use if DDR2 very well.You already mentioned the power issue, with 1.8V for DDR2. That is something AMD needed in the mobile arena to stay competitive, so if they were already designing a top notch DDR2 controller, might as well do the entire cpu line. Since much of the market is actually starting to shift to mobile solutions, from a growth standpoint, being competitive here is going to be telling in each company's numbers. Since Merom is having heat issues (hence why Conroe is coming out so far ahead of Merom, meaning less of a heat budget constraint) you can expect that Turion X2's with DDR2 will put some pain on Yonah machines. I suspect that AMD knows their bandwidth is superb with DDR2 and are designing Turion X2's with 512 cache because it doesn't hurt them much. Watch this area in 2006, because the world won't be painted blue if AMD does well here. Intel is likely well aware and will push as hard as possible to bring Merom out to keep AMD from making ground. Mobile designs under S1 socket are coming aplenty.
$.02
coldpower27 - Monday, April 10, 2006 - link
I must have missed it by what clock rate and what amount of cach were the models used???
Anand Lal Shimpi - Monday, April 10, 2006 - link
We purposefully didn't publish this information to protect our source of the CPU.Take care,
Anand
flyck - Monday, April 10, 2006 - link
well ofcourse we don't know the clock. But it is an important factor. @ 1.8GHz A64 didn't bennifit from dual channel. but it think @ 2.8GHz that story was totally different. So if you are testing @ 2.4GHz. there could be a larger gap @ 3GHz for example.Anand Lal Shimpi - Monday, April 10, 2006 - link
Very true, but from what I've seen the picture doesn't change much from the 3800+ up to the FX-62, at least with current CPUs/platforms. The main thing that shows a performance difference is when going to even lower latency memory. You are right though, the hungrier the CPU gets (faster clock, wider core, etc...) the more it depends on a high bandwidth memory bus. However, I do believe that AMD's own model numbers tell the tale of what to expect.I think that at the end of the day the 2 - 7% increase range is what will hold, with the vast majority of applications falling at the 2% end of the spectrum.
Take care,
Anand
ozzimark - Monday, April 10, 2006 - link
though one thing to keep in mind: memory efficiency is directly related to the cpu mhz. i've found that going from 2ghz to 3ghz while keeping the ram at 250mhz increases bandwidth by around 1800mb/s on my s939 rig :eek:Sunrise089 - Monday, April 10, 2006 - link
I think there will be a lot of current users taking the upgrade path in my subject line, or something close to it. I may very well buy a new AMD chip in 2007, I'd sure like to be able to, but for the next 12 months I only see myself buying a used, overclock proven 2x1meg cache s939 X2 at the end of summer, and then trading up to Conroe during the holidays. I can't really see anyone but the strongest fanboys (and I'm pretty strong) buying AM2.AnnonymousCoward - Monday, April 10, 2006 - link
Why in the world do you upgrade so often? My path might be AthlonXP 1800+ --> Conroe.