Does AM2's Performance Make Sense?
Assuming for a moment that the performance we're seeing here today is representative of what AMD will show off in 2 months, does it make sense? AMD has effectively doubled their memory bandwidth but they've seen virtually no increase in performance, other than in some very isolated situations.
If you'll remember back to the introduction of AMD's Revision E core, we did an article about how the new core brought support four new memory dividers allowing you to run at speeds up to DDR500 without overclocking your CPU or the rest of your system. In that article we looked at the overall performance benefit of DDR-500 over DDR-400 on a Socket-939 platform in a variety of situations. A recap of our performance results is below:
| Benchmark | Socket-939 (DDR-400) | Socket-939 (DDR-480) | % Advantage (DDR-480) |
| Multimedia Winstone 2004 | 41.9 | 42.7 | 2% |
| 3dsmax 6 | 2.78 | 2.80 | 1% |
| DivX 6.0 | 50.6 fps | 53.2 fps | 5% |
| WME9 | 4.22 fps | 4.28 fps | 1% |
| Quake 3 (10x7) | 121.9 fps | 127.2 fps | 4% |
| ScienceMark 2.0 (Bandwidth)* | 5378 MB/s | 5851 MB/s | 9% |
As you can see, given almost a 9% increase in memory bandwidth, we saw similarly small increases in overall performance. It would seem that the Athlon 64, at its current clock speeds, just simply isn't starved enough for memory bandwidth to benefit from an increase in bandwidth. You'll also see that the areas where faster DDR memory helped back then are pretty much the areas where DDR2-800 is showing gains today.
Based on our results from back then, if a 9% increase in memory bandwidth doesn't increase performance tremendously, then the 35% increase in bandwidth we see with DDR2-800 on AM2 shouldn't yield any more of a performance increase. Or simply put, yes, our AM2 performance numbers 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 $90 in memory plus a premium in boards and processor prices.
sprockkets - Monday, April 10, 2006 - link
I mean ddr2-800flemlion - Monday, April 10, 2006 - link
This seems to be just a quicky review. In the conclusion it is mentioned that the usefullness of memory bandwith increases as the CPU clock speed increases. But still a lower speed was used for this test than for the DDR1-400 versus DDR1-500 evaluation. It seems to me at least this test should either have been done at different speeds to get a feel of this impact or at minimum at the same speed of the DDR1-400 versus DDR1-500 article.As a sidenote, it's also interesting to see that the test config has no mention of the CPU speed that was used. If this is NDA, then say so, if not it just appears as hiding the details that would expose this article as gossip instead of information.
andrewln - Monday, April 10, 2006 - link
I meant...Intel will see how the next generation of AMD works just 5% faster....wouldn't they tune down conroe to match or make it just a bit faster than AMD and sell at the premium price? Since the demand will be almost the same.
1) AMD fanboi will keep on buying AMD
2) Intel fanboy will keep on buying Intel
3) But this time, people that wants performance, will be buying Intel (even though its only a 10% faster than the competitor, or 40$)
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.
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?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
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.
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
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 :)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.