The Opteron 6276: a closer look
by Johan De Gelas on February 9, 2012 6:00 AM EST- Posted in
- IT Computing
- CPUs
- Bulldozer
- AMD
- Opteron
- Cloud Computing
- Interlagos
Making Sense of the New Interlagos Opteron
This second look at the current Xeon and Opteron platforms added OLAP, ERP, and OLTP power and performance data. Combine this with our first review and the other publicly available benchmark and power data and we should be able to evaluate the new Opteron 6200 more accurately. So in which situations does the Opteron 6200 make sense? We'll start with the perspective of the server buyer.
Positioning the Opteron 6276
First let's look at the pricing. The Opteron 6276 is priced similar to an E5649, which is clocked 5% lower than the X5650 we tested. If you calculate the price of a Dell R710 with the Xeon E5649 and compare it with a Dell R715 with the Opteron 6276 with similar specs, you end up more or less the same acquisition cost. However, the E5649 is an 80W TDP and should thus consume a bit less power. That is why we argued that the Opteron 6276 should at least offer a price/performance bonus and perform like an X5650. The X5650 is roughly $220 more expensive, so you end up with the dual socket Xeon system costing about $440 more. On a fully speced server, that is about a 10% price difference.
The Opteron 6276 offered similar performance to the Xeon in our MySQL OLTP benchmarks. If we take into account the hard to quantify TPC-C benchmarks, the Opteron 6276 offers equal to slightly better OLTP performance. So for midrange OLTP systems, the Opteron 6276 makes sense if the higher core count does not increase your software license. The same is true for low end ERP systems.
When we look at the higher end OLTP and the non low end ERP market, the cost of buying server hardware is lost in the noise. The Westmere-EX with its higher thread count and performance will be the top choice in that case: higher thread count, better RAS, and a higher number of DIMM slots.
AMD also lost the low end OLAP market: the Xeon offers a (far) superior performance/watt ratio on mySQL. In the midrange and high end OLAP market, the software costs of for example SQL Server increase the importance of performance and performance/watt and make server hardware costs a minor issue. Especially the "performance first" OLAP market will be dominated by the Xeon, which can offer up to 3.06GHz SKUs without increasing the TDP.
The strong HPC performance and the low price continue to make the Opteron a very attractive platform for HPC applications. While we haven't tested this ourself, even Intel admits that they are "challenged in that area".
The Xeon E5, aka Sandy Bridge EP
There is little doubt that the Xeon E5 will be a serious threat for the new Opteron. The Xeon E5 offers for example twice the peak AVX throughput. Add to this the fact that the Xeon will get a quad channel DDR3-1600 memory interface and you know that the Opteron's leadership in HPC applications is going to be challenged. Luckily for AMD, the 8-core top models of the Xeon E5 will not be cheap according to leaked price tables. Much will depend on how the 6-core midrange models fare against the Opteron.
The Hardware Enthusiast Point of View
The disappointing results in the non-server applications is easy to explain as the architecture is clearly more targeted at server workloads. However, the server workloads show a very blurry picture as well. Looking at the server performance results of the new Opteron is nothing less than very confusing. It can be very capable in some applications (OLTP, ERP, HPC) but disappointing in others (OLAP, Rendering). The same is true for the performance/watt results. And of course, if you name a new architecture Bulldozer and you target it at the server space, you expect something better than "similar to a midrange Xeon".
It is clear to us that quite a few things are suboptimal in the first implementation of this new AMD architecture. For example, the second integer cluster (CMT) is doing an excellent job. If you make sure the front end is working at full speed, we measured a solid 70 to 90% increase in performance enabling CMT (we will give more detail in our next article). CMT works superbly and always gives better results than SMT... until you end up with heavy locking contention issues. That indicates that something goes wrong in the front end. The software applications that do not scale well could be served well with low core count "Valencia" Opteron 4200s, but when we write this, the best AMD could offer was a 3.3GHz 6-core. The architecture is clearly capable of reaching very high clockspeeds, but we saw very little performance increase from Turbo Core.
What we end up with then is more questions. That means it's time for us to do some deep profiling and see if we can get some more answers. Until then, we hope you've enjoyed our second round of Interlagos benchmarking, and as always, comments and feedback on our testing methods are welcome.
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Scali - Saturday, February 11, 2012 - link
"It also reduces throughput."No, it improves throughput, assuming we are talking from improvement going from 1 physical core to 2 logical cores.
Clearly two logical cores (on the same physical core) have less throughput than two physical cores, but that's obvious since you only have half the hardware.
And that, together with the fact that Intel's SMT chips have far better single-threaded performance to begin with, results in very good performance per die area (you know, that thing that people used to praise AMD GPUs for).
"Yes, it does, via the implementation of all that shared hardware on the chip."
You can't say that, since there is no non-modular version of Bulldozer (just as there is no non-HT version of the Intel architectures).
However, if you compare a 4-core HT architecture with a non-HT architecture, be that a Core2 Quad or a Phenom X4, Intel's transistorcount is clearly in the same ballpark, so HT does not add much in terms of transistorcount.
With CMT we see little or no indication of reduced transistorcount. AMD's 4-module chips are MUCH larger than regular 4-core chips have been. In fact, AMD"s 4-module design is even larger than Intel's 6-core design with HT.
"Two different approaches to the same idea."
I disagree. SMT is a very different idea from CMT (which is a bogus marketing term invented by AMD anyway). CMT is more of a marketing excuse for not having proper SMT, and shows no merit in actual silicon.
"but I don't think we can label one as inherently better than the other yet."
Well clearly we disagree on that then.
I think SMT is clearly inherently better than CMT. SMT has far more flexible sharing of resources than AMD's half-baked approach.
And any theoretical disadvantages (fighting over resources and all that) can be put to bed with benchmarking such as in this review: the disadvantages may exist, but the net performance is unbeatable anyway. A midrange Xeon schools a CMT-based chip of twice the size.
Andexxx - Wednesday, February 15, 2012 - link
Well, there are a lot of factors affecting single-threaded performance in real life. So CMT indeed has its scaling advantages as tests suggested. At least most of the things should be constant when comparing CMT-on and CMT-off, while comparing SMT and CMT on different implementations is not. Lack of single-threaded performance is not a valid point of blaming CMT.If you want to *proof* CMT is a half-baked marketing crap while SMT is the only solution, what you need is a SMT-based AMD BD monolithic core or a CMT-based Intel monolithic module for comparison.
For the transistors counting, well, that's their choice of making such a cache and uncore configuration. You can keep telling 4-module chip is blahblahblah, but in some cases it beats a 4C8T Xeon chips. Transistors is not a big matter from customer viewpoint but just the producer viewpoint. If you want to argue with GPU's performance metrics, GPU is a data-parallel processor with bunch of logic units, while CPU is a latency-sensitive girlfriend of caches. Large amount of cache can make your Performance/mm^2 or Performance/transistors look worse. So trade-offs on the amount of cache should have been done before they started to design the chip.
Scali - Wednesday, February 15, 2012 - link
Well, one of the reasons why AMD's current CPUs have such poor single-threaded performance is because they moved from 3 ALUs per thread to 2 ALUs per thread.This is part of the whole CMT design.
So in that sense, CMT can be blamed for the poor single-threaded performance at least.
And since single-threaded performance is so bad, it is only logical that scaling to more threads is relatively good.
On a CPU with faster single-threaded performance, you run into IO limits sooner (memory, disk etc), so it is more difficult to maintain similar scaling with increased thread count.
The strength of SMT is that Intel did not have to cut any ALUs when implementing HT. Pentium 4 Northwood with HT still had two double-pumped ALUs, like the non-HT Willamette that went before it.
Likewise, Core i7 still has 3 ALUs, like Core2.
Another strength of SMT is that even with one less ALU per 2 threads than CMT, it still reaches similar performance in multithreaded scenarios. CMT can not share these ALUs between threads, while SMT can.
Conclusion: CMT is nonsense.
For the full version, see: http://scalibq.wordpress.com/2012/02/14/the-myth-o...
slycer.tech - Monday, February 13, 2012 - link
If Bulldozer arc really bad, how about this?http://www.marketwatch.com/story/amd-opterontm-620...
Can someone prove this award is a big liar?
duploxxx - Tuesday, February 14, 2012 - link
read the article, the baseline they use for price/performance is based on spec results....lots of companies still use these results to decide on a platform.but then again, benchmarks don't always show the real world value or even hard to compare since many have in house applications that don't scale or scale different like the ones benchmarked in reviews. 90% of the datacenters don't even require more then any midrange cpu, anything above midrange is wasted money and both vendors provide more then adequate solutions to that. It's the human mind that is often blocking sanity. Investing that wasted money in other solutions often provide a better total performing solution.
anti_shill - Monday, April 2, 2012 - link
shill_detector by anti_shill on Monday, April 02, 2012Here's a more accurate reflection of Bulldozer/ interlagos performance, untainted by intel ad bucks...
http://www.phoronix.com/scan.php?page=article&...
But if u really want to see what the true story is, have a look at AMD's stock price lately, and their server wins. They absolutely smoke intel on virtualization, and anything that requires a lot of threads. It's not even close.