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Intel P4 Hyper-Threading Technology:

Intel’s Hyper-Threading Technology allows a single physical Processor to execute multiple threads (instruction streams) simultaneously, potentially providing greater throughput and improved performance.

Quoting Microsoft: "Hyper-Threading Processors contain two architectural states on a single Processor core thus making each physical Processor act as two logical Processors for the OS. The two logical Processors still share the same execution resources of the Processor core. Hyper-Threading Processor performance gains do not approximate having two complete, physical Processors.

Hyper-Threading Technology complements symmetric multi-processing (SMP) by allowing more threads to execute simultaneously per processor."

1. GIGABYTE - Motherboard - FAQ: "PowerDVD 4.0 for XP can't work with Hyper Threading function enable." Solution - Get PowerDVD Patch. (12/8/2003)
2. 815227 - Performance Degradation Occurs in the UnmapViewOfFile Function: "This problem occurs if you install Windows XP Service Pack 1 (SP1) on an Intel Pentium 4 computer that has more than one logical Processor."
3. Windows Support for Hyper-Threading Technology: DL White paper detailing Windows support for Hyper-Threading Technology (5/1/2003).
4. Microsoft Windows-Based Servers and Intel Hyper-Threading Technology: Windows Based Servers - Addresses Win2000 Server through WinServer 2003. DL Hyper-Threading Doc file.
5. Microsoft SQL Server Microsoft SQL Server and Intel Hyper-Threading Technology:
6. 810231 - INFO Windows XP and Hyper-Threading: "When Hyper-Threading is enabled in the computer's BIOS, Windows XP automatically upgrades the hardware abstraction layer (HAL) if it must use a multi-processor HAL, and an additional processor or processors may be installed and listed under Processors in Device Manager. The system will prompt you to restart so that the new settings can take effect."
7. 811366 - Cannot Select MPS Uniprocessor or ACPI Uniprocessor HAL: "If you remove a processor from a multiprocessor computer or turn off Hyper-Threading support in the BIOS, and then try to change your Hardware Abstraction Layer (HAL)..."
8. 812035 - A Crash Occurs in Ks.sys on Computers with Intel Hyper-Threading CPU:
9. Hyper-Threading Implications and Setup on Microsoft Operating Systems:

   Quoting Intel, quoting Microsoft Licensing...
   Win2000 Operating Systems can detect Hyper-Threading Technology enabled Processors, but it has not been fully optimized for their support. The Windows XP and .NET operating systems have been optimized for the support of Hyper-Threaded processors. Windows 2000 and Windows XP (and .NET server) operating systems count the number of CPUs differently. Windows 2000 counts all logical processors in the system towards the processor license limits. Windows XP and .NET count only the physical processors. The license limits are given in the following table.

10. Intel Developer Services - Multithread Execution on One Physical Processor:
11. Intel Home Computing - Component Guide Operating System:

    Below quoted from Intel...

    The Operating System must be capable of supporting a multi-threaded, single Processor environment in order to use Hyper-Threading Technology.
    
    The following Operating Systems have been optimized for Hyper-Threading Technology:
    
     WinXP Pro
     WinXP HE
     Linux version 2.4.x (and higher) Further details, see below.
    
    The following Operating Systems are compatible with Hyper-Threading Technology, but may require additional steps to enable multi-threading. If you are using one of the following operating systems, it is required that you re-install the operating system.
    
     Win2000 (all versions)
     WinNT 4.0 (limited driver support)
    
    The following Operating Systems do not support Hyper-Threading Technology. If you are using one of the following operating systems, it is advised that you should disable Hyper-Threading Technology in the system BIOS Setup program.
    
     WinMe
     Win98 (limited driver support)
     Win98SE

12. Hyper-Threading Technology - Determining if HT Technology is Enabled:

    Using WinXP HE or WinXP Pro - We have two ways to determine if Hyper-Threading Technology is enabled without rebooting to enter the BIOS setup.
    

    1. Task Manager: Press - CTRL-ALT-DELETE, click Performance tab. See two CPU Windows.
    2. Device Manager: Open Device Manager, click on Processors. See two Processors Listed.

     

13. Hyper-Threading Technology - OS - Optimizations for Hyper-Threading Technology:

    Windows Operating System Desktop Based PCs
    Desktop Operating Systems including optimizations for HT Technology currently eligible to carry the new Intel P4 Processor with HT Technology logo:

    1. WinXP Pro
    2. WinXP HE
    
    Desktop Operating Systems not recommended for use with Hyper-Threading Technology. If you are using one of the following Desktop Operating Systems, it is advised that you should disable Hyper-Threading Technology in the System BIOS Setup program:
    
    1. Win2000 (all versions)
    2. WinNT 4.0
    3. WinMe
    4. Win98
    5. Win98SE
    
    Linux Operating System Desktop Based PCs
    The following Linux Operating Systems include optimizations for HT Technology and are currently eligible to carry the Intel Pentium 4 Processor with HT Technology logo:
    1. Red Hat Linux 9 (Professional and Personal versions)
    2. SuSE Linux 8.2 (Professional and Personal versions)
    3. Red Flag Linux Desktop 4.0
    4. COSIX Linux 4.0 (Slow link)
14. www.theinquirer.net - Microsoft warns Intel hyperthreading no panacea: Counting Processors...
15. www.theinquirer.net - Microsoft re-words Intel Hyperthreading support: "...no Windows OS will support "logical" Processors unless the Hyper Threading is started by the BIOS and identified by MADT."
16. Intel.com - Hyper-Threading Technology for the Desktop: Intel Hyper-Threading Technology Requirements
17. developer.intel.com - Hyper-Threading Technology: "Hyper-Threading Technology provides thread-level-parallelism (TLP) on each processor resulting in increased utilization of processor execution resources. As a result, resource utilization yields higher processing throughput. Hyper-Threading Technology is a form of simultaneous multi-threading technology (SMT) where multiple threads of software applications can be run simultaneously on one processor."
18. Hyper-Threading Technology - Frequently Asked Questions:
19. Intel Developer Services - Hyper-Threading Technology:
20. Intel Developer Services - Windows:
21. Intel Developer Services - Improved Security and Performance with Microsoft Windows XP and Hyper Threading Technology: "On an HT Technology enabled System, XP manages Processor Resources so that security features run on one logical Processor and front-end applications run on a second logical Processor (both housed on the same physical Processor)."
22. Intel Software Development Products: Thread Checker.
23. Pentium 4 Processors - Integration Overview: