Update for Windows 2003 x64 Edition – KB899656 — On some multi-processor x64 systems, Windows Server 2003 SP1 does not correctly recognize all configured processors when hyper-threading is enabled. This occurs when the BIOS has been designed to reprogram the APIC (advanced programmable interrupt controllers) ID’s at boot time. Most x64 systems are not affected. Do not install this update unless you are experiencing the stated problem.

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