Bulldozer for Servers: Testing AMD's "Interlagos" Opteron 6200 Series

Conclusions

To help summarize the current situation in the server CPU market, we have drawn up a comparison table of the performance we have measured so far. We'll compare the new Interlagos Opteron 6276 against the outgoing Opteron 6174 as well as teh Xeon X5650.

Let us first discuss the virtualization scene, the most important market. Unfortunately, with the current power management in ESXi, we are not satisfied with the Performance/watt ratio of the Opteron 6276. The Xeon needs up to 25% less energy and performs slightly better. So if performance/watt is your first priority, we think the current Xeons are your best option.

The Opteron 6276 offers a better performance per dollar ratio. It delivers the performance of $1000 Xeon (X5650) at $800. Add to this that the G34 based servers are typically less expensive than their Intel LGA 1366 counterparts and the price bonus for the new Opteron grows. If performance/dollar is your first priority, we think the Opteron 6276 is an attractive alternative.

And then there is Windows Server 2008 R2. Typically we found that under heavy load (benchmarking at 85-100% CPU load) the power consumption was between 3% (integer) to 7% (FP) higher on the Opteron 6276 than on the Xeons and Opteron 6100, a lot better than under ESXi. Add to this the fact that the new Opteron energy usage at low load is excellent and you understand that we feel that there is no reason to go for the Opteron 6100 anymore. Again, AMD still understands that it should price its CPUs more attractive than the competition, so from the price/performance/watt point of view, the Opteron 6276 is a good cost effective alternative to the Xeon...on the condition that you enable the "high performance" policy and that AMD keeps the price delta the same in the coming months.

That is the good news. We cannot help but to feel a bit disappointed too. AMD promised us (in 2009/2010) that the Opteron 6200 would be significantly faster than the 6100: "unprecedented server performance gains". That is somewhat the case if you recompile your software with the latest and greatest optimized compiler as AMD's own SPEC CINT (+19%), CFP 2006 (+11%) and Linpack benchmarks (+32%) show.

One of the real advantages of a new processor architecture (prime examples where the K7 and K8) is if it performs well in older software too, without requiring a recompile. For some people of the HPC world, recompiling is acceptable and common, but for everybody else (that is probably >95% of the market!), it's best if existing binaries run faster. Administrators generally are not going to upgrade and recompile their software just to make better use of a new server CPU. Hopefully AMD's engineers have been looking into improving the legacy software performance of their latest chip the last few months, because it could use some help.

On the other side of the coin, it is clear that some of the excellent features of the new Opteron are not leveraged by the current software base. The deeper sleep and more advanced core gating is not working to its full potential, and the current operating systems frequently don't appear to know how to get the best from Turbo Core. The clock can be boosted by 39% when half of the cores are active, but an 18% boost was the best we saw (in a single-threaded app!). Simply turning the right knobs gave some tangible power savings (see ESXi) and some impressive performance improvements (see Windows Server 2008).

In short, we're going to need to do some additional testing and take this server out for another test drive, and we will. Stay tuned for a follow-up article as we investigate other options for improving performance.