snydeq writes "Windows XP, Windows Vista, and (soon) Windows 7 all support SMP out of the box, but as InfoWorld's Randall Kennedy notes, 'experience has shown that multiprocessing across discrete CPUs is not the same thing as multiprocessing across integrated cores within the same CPU.' As such, Kennedy set out to stress the multiprocessing capabilities of Windows XP, Windows Vista, and Windows 7 in dual-core and quad-core performance tests. The comprehensive, multiprocess workload tests were undertaken to document scalability, execution efficiency, and raw performance of workloads. 'What I found may surprise you,' Kennedy writes. 'Not only does Microsoft have a firm grasp of multicore tuning, but its scalability story promises to keep getting better with time. In other words, Windows Vista and Windows 7 are poised to reap ever greater performance benefits as Intel and AMD extend the number of cores in future editions of their processors.'"