New Opteron Servers Struggle Badly Despite Additional Cores

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News Posted: Wed, Nov 23 2011 11:45 AM
In the wake of Bulldozer's weak desktop launch, there was some hope that server benchmarks would redeem the chip and give AMD a fighting chance against Intel in at least one of its three core markets. Recent reviews and a comprehensive roundup of formally published results, however, indicate that while BD fares a bit better in servers, it's far from vindicated.

AMD's new 6200 Opterons (Interlagos) are often a sidewise move from the older 6100 series, which is based on Magny-Cours. Interlagos is essentially trapped by the same trio of issues that cripple Bulldozer. The shared core design hurts SMP scaling; a 16-core Interlagos scales more like a 13-14 core Magny-Cours. The clock speed increases are offset by Bulldozer's lower single-thread performance. Finally, Interlagos draws more power than its predecessor, which in turn prevents further clock speed scaling.

As Ars Technica notes, Interlagos is faster than its predecessor in some tests -- but often by much less than one might expect. In JBB2005, Interlagos is just 27 percent faster than Magny-Cours, despite 33% additional cores and a four percent clock speed advantage.

This didn't exactly happen

Bulldozer / Interlagos' lowered IPC is at the heart of the CPU's problems. If AMD had even managed to maintain single-thread performance parity with Thuban, than the chip's higher clock speeds and greater number of cores would give it at least a marginal fighting chance, particularly in highly multithreaded environments. As Ars writes, "AMD compromised single-threaded performance in order to allow Bulldozer to run more threads concurrently, and that trade-off simply hasn't been worth it... it leaves us wondering what might have happened if AMD had simply extended its old architecture. Another four cores in a Magny-Cours processor would show close to the same 33 percent gain, and would do so without compromising single-threaded performance."

The same thought has occurred to us. Bulldozer/Interlagos was supposed to save die space compared to Magny-Cours, but AMD's decision to load the chip with 16MB of L2+L3 cache per eight-core configuration largely obviated the space savings. At this point, extending Thuban does look as though it would've been the smarter option.

The problem with that argument, however, is that it wouldn't have addressed the greater issue. While it's true that a 16-core Magny-Cours and subsequent 8-core 32nm desktop chips would've been more attractive than Bulldozer, they wouldn't have improved AMD's competitive position vs. Intel. Sunnyvale would still need a new CPU architecture that was capable of competing with Sandy Bridge, and it still wouldn't have one.

There's no quick fix for Interlagos, but there's still the possibility that future iterations of the chip will prove more capable. Right now, that -- and a handful of tepid server wins -- is the best AMD has to offer.
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AKwyn replied on Wed, Nov 23 2011 6:46 PM

A shame... It just seems like AMD can't get a break around here. However, I am hopeful that AMD will resolve it's problems and release a later iteration of Bulldozer that with the promised x86 performance increase in a slide I remember seeing.


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Underwhelm after underwhelm...I'm still hopeful AMD can stop this bad streak, even if I can't see how. By the time Bulldozer is fixed, Ivy Bridge will be out. Geewhiz.

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Really not surprising with the underwhelming performance of the bulldozer cores. Many cores on a server processor is a good thing because you can consolidate many servers onto one physical piece of hardware. Unfortunately for this to be plausible those cores have to perform reasonably.

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realneil replied on Sun, Nov 27 2011 8:33 PM

They just changed CEO's at that company. Maybe this Bulldozer Debacle has to do with the 'old news' CEO who is gone. What would the proper terminology be?,....residual fallout? Crying

Maybe they're gonna pull a Rabbit out of their hats soon.

Maybe they should,......

The thing is that I like AMD. I like supporting the underdog because I believe that Intel's prices will certainly go through the roof if they're gone and these parts are already too expensive as I see it.

They're really making it hard for me to support them lately. I will admit that my Fusion APU system is a great little PC and I really like the way it performs. But I want to see some High Performance, smokin' fast CPU's out of these guys too!



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