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AMD's Opteron Dual-Core Processors

The Plan

The elegance of AMD's dual-core CPU lies in the method used to link the two processing cores on the chip. The plan for the 64-bit chips included a dual-ported System Request Queue and Crossbar, technology designed to directly connect one processor/cache core--and, eventually, two of them--to the integrated memory controller and HyperTransport pipelines. Now that dual-core technology is available, the second port can be put to use.

As with earlier Opterons, the 875 chip has a dedicated memory controller, so every new processor socket added to a system board increases the memory bandwidth by another 144-bit, 6.4-GBps data path. Although the 875's two cores share the same memory controller, the vendor says this impacts memory performance by less than 10 percent.

AMD's approach differs dramatically from Intel's Hyper-Threading technology, which only emulates a second virtual processor and lets two threads execute in parallel on a single core. Although this has proved to be a good use of processing cycles, both threads share the resources of a single processor. Intel also has introduced a dual-core Pentium for the desktop, but the design requires an entirely new support chipset and continues to rely on Intel's aging front-side bus technology.


Good

• Well-planned, high-performance architecture
• Backward-compatible with existing chipsets
• Excellent 32- and 64-bit performance
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