Does AM2 Reduce the Impact of L2 Cache Size?

We've already seen that Socket-AM2 doesn't really impact performance except for in games, but does the higher bandwidth memory controller reduce the impact of AMD's 1MB L2 cache parts compared to its 512KB L2 cache offerings? 

 Benchmark - Athlon 64 X2 2.0GHz Socket-939 (1MB vs. 512KB Advantage)  Socket-AM2 (1MB vs. 512KB Advantage)
Cinebench 9.5 Multi-Core Rendering Test 0.2% 0%
3dsmax 7 0.3% 0.6%
Adobe Photoshop CS2 2.7% 2.5%
DivX 6.1 0% 0%
WME9 0% 1%
Quicktime 7.0.4 (H.264) 0.9% 1.3%
iTunes (MP3) 0% 0%
Quake 4 - 10x7 (SMP) 4.8% 3.5%
Oblivion - 10x7 7.5% 3.3%
F.E.A.R. - 10x7 8.6% 6.2%


In the application benchmarks there isn't really a difference in how performance scales with cache size between the two platforms, but looking at the games there is indication of a pattern that is developing.

In Quake 4, Oblivion and F.E.A.R. the 1MB L2 cache seems to make slightly more of a difference on the Socket-939 platform than on the Socket-AM2 platform.  While the 1MB cache offers a 4.8%, 7.5% and 8.6% performance advantage in those three games on the Socket-939 platform, on AM2 the advantage is cut down to 3.5%, 3.3% and 6.2% respectively.  The explanation being that with a lower latency memory controller and more available memory bandwidth, the benefits of a larger cache are reduced on Socket-AM2. 

However the differences in performance scaling that we're seeing here are small enough that once you take into account the amount of variation you can see between runs, it's not really worth concluding anything concrete based on this data.  What we do see here is a trend of the 1MB L2 cache parts doing less on Socket-AM2 than on Socket-939 (another way of looking at it is that the 512KB are doing better on AM2 than they did on 939), but the margins are small enough that we can't really say for sure what is causing the trend.

Once again, the trend only seems to impact games, as the other application tests we've run appear to be basically unaffected. 

The Question on Everyone's Mind: Is AM2 Faster? How Does the New 4000+ Stack Up?


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  • Griswold - Tuesday, May 23, 2006 - link


    Okay, here's my guess for the stopgap solution...drum roll...L3 cache. I think AMD will release a 2.8 revised FX-62 with L3 cache or an ahead of schedule 3.0 GHz FX-64 with L3 cache. Just my guess.

    Sounds conceiveable indeed. Though, the latter option would probably blow TDP out of proportion on 90nm.
  • mlittl3 - Tuesday, May 23, 2006 - link

    Yeah, that is a problem but Anand did say "trick up its sleeve" so maybe they have one last 90 nm manufacturing process that's better than today's. I've read some articles about L3 cache coming for AMD and one article (take with grain of salt) that says AMD will ramp clock speeds fast. Maybe the trick will have something to do with these factors. Who knows? Reply
  • darkdemyze - Tuesday, May 23, 2006 - link

    Whatever it is I'm interested in reading about it Reply
  • Regs - Tuesday, May 23, 2006 - link

    Whatever it is, it's going to be expensive. Reply
  • TrogdorJW - Tuesday, May 23, 2006 - link

    Actually, I was sort of thinking that the "stopgap solution" might be to cut prices. God only knows that I would love to see a $200 X2 processor! Reply
  • Griswold - Tuesday, May 23, 2006 - link

    Well, they will have to drop prices at some point after core 2 is actually available. Reply
  • xFlankerx - Tuesday, May 23, 2006 - link

    Indeed, same results as expected. Maybe this will make the AMD fanboys shut up about "waiting to see what the final results are." NOTE: I have a AMD system, I'm simply addressing those that refuse to accept Conroe's superiority.

    Although...I must say that this "stop gap" solution by AMD has piqued my curiosity.

    But I believe that these say it perfectly;

    "One of its stipulations for sending out Socket-AM2 review kits was that the CPUs not be compared to Conroe."

    "We do get a sense of concern whenever Conroe is brought up around AMD."

    "So when Intel first started talking about its new Core architecture, we turned to AMD for a response that it surely must have had in the works for years, but as you all know we came up empty handed."

    Those just say it all for me. Seems like AMD's in trouble. From what I've been reading, K8L doesn't bring in architectural changes either. Sure you get Quad Cores, L3 cache, FB-DIMM support, DDR3, and faster HyperTransport, but if AMD doesn't improve on it's performance-per-clock efficiency, then Intel's Quad Cores (due almost 9 months before AMD's) are going to rule supreme yet again.
  • Griswold - Tuesday, May 23, 2006 - link


    Those just say it all for me. Seems like AMD's in trouble. From what I've been reading, K8L doesn't bring in architectural changes either.

    Maybe read up on it first.

    Memory mirroring, data poisoning, HT retry protocol support, doubled prefetch size (32byte instead of 16), 2x 128bit SSE units (instead of 2x 64bit), out of order load execution, Indirect branch predictors and a handful new instructions sure sounds like a few architectural changes and not just a simple revision stepping.
  • rADo2 - Tuesday, May 23, 2006 - link

    Sorry, links again:

    Intel Conroe @ 3.9GHz: SuperPI 1M - 12.984s">

    AMD FX-57 @ 4.2GHz: SuperPI 1M - 21.992s">
  • MadAd - Monday, May 29, 2006 - link

    Try measuring like for like and then come back with your silly benchmark comparison. EG use a superpi data size that will fit on BOTH cpus caches, not just conroes and then compare performance.

    With the FX57 having just a 1M cache its bullsht smoke and mirrors saying the 1M superpi is slower, o rly? perhaps thats because it takes more than 1M to hold both the feature and data sets on a 1M superpi.


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