Stress test: AMD Opteron Magny-Cours versus Intel Xeon Nehalem-EX

If the number of concurrent processes is large enough (think virtualization), then quad-CPU, 48-core AMD Opteron wins the price-performance race

As part of the testing of the Dell PowerEdge R815, I ran the 48-core AMD Opteron Magny-Cours server through my series of scaling, single-threaded, real-world benchmarks. I've been using these since the advent of multicore CPUs and have found that they do a good job of representing portions of common workloads.

All the tests are single-threaded, but they are run concurrently at increasing levels and measured by the time taken for all threads to complete, therefore providing a picture of CPU performance under a range of loads. There are seven tests in all, including LAME MP3 conversion of a 150MB WAV file, gzip and bzip2 compression and decompression tests, an increasingly irrelevant MD5 checksum test, and an MP4-to-FLV video conversion test.

[ The Dell PowerEdge R815 and its four 12-core AMD Opteron CPUs want to run many, many virtual machines, at a much lower cost than Intel multicore. See "InfoWorld review: Dell R815 server makes heavy virtualization light on the wallet." ]

The tests are scripted to run in a series of 8, 12, 24, 48, 96, and finally 128 concurrent instances. Several separate runs are conducted on local disk, and several on a ramdisk to pin more of the load on the CPUs rather than the disk I/O subsystem. The results displayed here were derived from the ramdisk tests.

The Dell PowerEdge R815 was pitted against a similarly equipped server with two Intel Nehalem-EX X7560s and the same amount of RAM. On the face of it, this might seem like an odd comparison, because the Nehalem-EX system had only 16 cores (8 cores in each of two CPUs), while the R815, based on AMD Opteron 6174 Magny-Cours processors, had 48 cores (12 cores in each of four CPUs). Lacking a system with four Nehalem-EX CPUs, I couldn't do a quad-to-quad test, but these numbers are still significant for a very different reason: The quad-CPU R815 is several thousand dollars cheaper than the dual-CPU Intel based server. In terms of bang for your buck, these tests are very relevant.

The results were about what I expected. Although the clock speeds are similar between the two sets of CPUs, the Intel Nehalem-EX server outpaced the R815 in most tests when the concurrency levels were at or below physical core counts. However, once the concurrency levels eclipsed the physical core counts, the R815 pulled ahead dramatically. Also, the R815 maintained the same level of performance in all tests at or below physical core counts. Once the concurrency levels reached two to three times the number of Intel cores, the R815 completed the more difficult LAME MP3 and MP4-to-FLV conversion tests far faster than the Nehalem-EX box.

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