AMD's Opteron finds a new gear

At Opteron’s two-year anniversary gathering in New York on April 21, 2005, AMD rolled out its first dual-core Opteron CPU. Not only do the new chips turn dual-processor workstations and servers into four-processor workhorses, but the upgrade path for customers with existing Opteron systems redefines “painless.” You merely pop the dual-core parts into your current Opteron server, and they will run the same software you’re running now. Scale-up -- a cost-effective internal upgrade path previously reserved for larger systems -- is now within reach of entry-level server buyers.

“Dual core” refers to the placement of a second CPU on a single physical chip. The two cores are full-fledged Opterons sitting side by side on a chip that’s exactly the same size as the single-core Opteron. Dual-core systems will be most attractive to those who have an eight-cylinder appetite but only a four-cylinder budget. But dual core is no bargain if it shortchanges customers on performance. AMD told us that the second core delivers a 70 percent to 90 percent performance improvement to multiprocessor applications. If AMD’s claims prove accurate, then dual core will be a good investment even for those who can afford quad-processor machines.

Never one to take a vendor’s word for anything, I built a reference system from the new Opteron components and began running it through a battery of standardized performance tests. AMD supplied me with a pair of production dual-core Opteron 875 2.2GHz CPUs and an Opteron workstation motherboard from Tyan, the Thunder K8WE model S2895. My testing continues as this article goes to press, but enough results are in to provide a snapshot of the performance of the dual-core Opteron relative to its single-core cousin.

The nitty-gritty

For benchmark tests I chose an old favorite: the CPU2000 suite from Standard Performance Evaluation Corporation Corp. (SPEC). The test scripts were compiled using Intel’s compilers for EM64T (Extended Memory 64 Technology) and were run on Windows Server 2003 Enterprise x64 Edition. The SPEC software is mature and well-organized, and it creates consistent results across platforms. Past test results submitted by vendors are open to public scrutiny at spec.org, and to SPEC’s credit, full disclosure of the testing conditions is required.

CPU2000’s two components, SPECint2000 and SPECfp2000, measure integer and floating-point performance, respectively. Integer tests exercise system calls, application performance, memory management, and OS scheduling efficiency more than they show off how fast your machine multiplies whole numbers. In contrast, the floating-point benchmarks are all about pushing your CPUs to the edge of their performance and environmental (power, cooling, and noise) limits.

The tests referenced in the table are subsets of SPEC’s SPECint_rate2000 and SPECfp_rate2000 tests. Rate tests launch multiple simultaneous processes -- ideally, and in this case, one benchmark process per core -- to see how smoothly a system scales to handle a rising workload. If a system scaled perfectly, doubling the number of processes (or cores) would make it capable of handling twice as much work with no degradation in performance, producing CPU2000 rate test results roughly double that of the original configuration.