The following overview and integration instructions are for professional system integrators building PCs that use boxed Intel® desktop processors supporting Hyper-Threading Technology1 with industry-accepted motherboards and peripherals. It contains technical information specific to boxed Intel® desktop processors and supporting Hyper-Threading Technology and is intended to aid in system integration. To determine if your processor supports Hyper-Threading Technology1 consult the Product Specifications and Comparisons. Note: Before building a boxed Intel desktop processor-based system, consult the motherboard manual, boxed processor manual, and the relevant integration overview for your processor (the following information is intended to be supplementary to these documents). Boxed Intel processor product information can also be found in the processor Product Brief, Frequently Asked Questions, and Selling Guide.
Table of Contents
Hyper-Threading Technology OverviewPlatform Component Requirements
- Processor Selection
- Motherboard Selection
- Operating System Support
- Hyper-Threading Technology Branding Tool
Verifying Hyper-Threading Technology in Windows* XP
Software Considerations
Additional Information
Hyper-Threading Technology Overview
Intel introduced the advancement of Hyper-Threading Technology to the desktop computing platform with the Pentium 4 processor. This technology, coupled with the existing Intel® NetBurst™ microarchitecture, is designed to deliver superior performance for even the most demanding applications and environments. The Pentium 4 processor brand name reflects breakthrough technology and performance that combines innovative new features with proven Intel quality.
Hyper-Treading Technology enables a single physical processor to execute two separate code streams (called threads) concurrently, increasing processor utilization and providing greater throughput and improved performance. Architecturally, the Intel processor supporting Hyper-Threading Technology consists of two logical processors (see Figure 1), each of which has its own architectural state. The architectural state that is duplicated for each logical processor consists of the data registers, segment registers, control registers, debug registers, and most of the MSRs or Model Specific Registers. Each logical processor also has its own advanced programmable interrupt controller or APIC. After power-up and initialization, each logical processor can be individually halted, interrupted, or directed to execute a specified thread, independently from the other logical processor on the Pentium 4 processor core.
Figure 1. Comparison of a Intel® Processor Supporting Hyper-Threading Technology and a Traditional Dual Processor System
Unlike a traditional dual processor (DP) configuration that uses two separate physical processors (see Figure 1), the logical processors in an Intel processor supporting Hyper-Threading Technology share the execution resources of the processor core (see Figure 2), which include the execution engine, caches, system bus interface, and the firmware. Hyper-Threading Technology is designed to improve the performance of Intel processors by maximizing the use of available execution resources in the Intel® NetBurst™ microarchitecture, and exploiting the multi-threaded nature of contemporary operating systems (see Operating System Support).
Figure 2. Intel® NetBurst™ Microarchitecture Duplicated and Shared Resources for Intel® Processors Supporting Hyper-Threading Technology
Most contemporary operating systems (including Microsoft* Windows* XP and certain versions of Linux*; See Operating System Support for details) divide their workload into processes and threads that can be independently scheduled and dispatched to run on two or more processors. The same division of workload can be found in many multi-threaded applications. Hyper-Threading Technology leverages the process- and thread-level parallelism found in contemporary operating systems and multi-threaded applications by allowing threads to be executed on separate logical processors. Instructions from both threads are simultaneously dispatched for execution by a single Intel processor using out-of-order instruction scheduling to keep as many of its execution units as possible busy during each clock cycle. Multi-tasking environments can also benefit from Hyper-Threading Technology. Concurrent applications can resemble multi-threaded application workloads to the processor, as each program issues an independent thread for execution. Hyper-Threading Technology provides increased processing efficiency which is passed on to the PC user in the form of better responsiveness and immediate performance when running concurrent applications.
To understand how Hyper-Threading Technology improves resource utilization, Figure 3 shows an example comparing a traditional single processor (SP) system (Figure 3A), traditional dual processor (DP) system (Figure 3B), and a system based on a Pentium 4 processor supporting Hyper-Threading Technology (Figure 3C). The SP system contains one superscalar processor that can execute up to three instructions every cycle and allows a single thread ("Thread 1", shown in orange) to be executed on this single (or physical) processor. The DP system contains two superscalar processors that can each execute up to three instructions every cycle and allows two separate threads to be executed on each (physical) processor ("Thread 1" and "Thread 2", shown in orange and blue respectively). As shown in Figure 3A and 3B, each box within each processor represents an execution unit. Each set of three horizontal boxes within each processor shows how the three execution units are being used during a given clock cycle. If a box is white, that execution unit is idle during the given clock cycle (for example, if one box is white during a clock cycle, then 1/3 of the resources are idle and 2/3 of the resources are utilized during that clock cycle). The vertical sets indicate the utilization of the three execution units over time (during multiple clock cycles). The more white boxes, the less efficient the utilization of execution resources. Sometimes all the execution resources within a processor are being used, and sometimes there are idle resources that are waiting due to cache misses, branch mispredictions, or instruction dependencies for each thread.
Figure 3 shows the result of system based on an Intel processor supporting Hyper-Threading Technology. This configuration allows the Intel processor supporting Hyper-Threading Technology to execute two separate threads simultaneously ("Thread 1" and "Thread 2", shown in orange and blue respectively), one thread for each logical processor. The Intel processor supporting Hyper-Threading Technology is utilizing the execution units more frequently and reducing idle time on the processor. Resource utilization can increase significantly for the Intel processor supporting Hyper-Threading Technology, but it is dependent on how each application is designed to use threading and the resources with the processor. For example, if an application is multi-threaded in such a way that different threads can use different resources in parallel (such as scheduling integer computation-intensive work on one logical processor while running floating-point computations on the other), then throughput for the processor can increase significantly. Intel processors supporting Hyper-Threading Technology increase instruction processing throughput and can take advantage of otherwise idle processor resources, which improve performance on both multi-threaded applications and multi-tasking environments.
Figure 3. Comparison of Execution on a Traditional Single Processor System, a Traditional Dual Processor System, and a Pentium® 4 Processor-based System Supporting Hyper-Threading Technology
(Note: This figure is a demonstration of the concepts underlying Hyper-Threading Technology and does not attempt to show the resource utilization patterns of any existing processors or software application.)
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Section Contents
Enabling Hyper-Threading Technology on an Intel processor-based system requires all of the following platform components:
- Intel® processor supporting Hyper-Threading Technology
- Motherboard that supports Hyper-Threading Technology
- Operating system that includes optimizations for Hyper-Threading Technology
The above requirements are specific to integrating Intel processor-based systems supporting Hyper-Threading Technology. Note: Before building an Intel processor-based system, consult the motherboard manual, boxed processor manual, and the relevant integration overview (the following information is intended to be supplementary to these documents).
Processor Selection
Intel processors supporting Hyper-Threading Technology can be identified using the Product Specifications and Comparisons.
Motherboard Selection
Motherboards used with an Intel processor supporting Hyper-Threading Technology must utilize a chipset which supports the Intel NetBurst microarchitecture and Hyper-Threading Technology. Table 1 shows a listing of Intel® Chipsets which support the Intel NetBurst microarchitecture and Hyper-Threading Technology. Note: Ensure that you are using a motherboard that supports the specified system bus speed for your processor system bus. Failure to use an appropriate motherboard may result in running your processor out of specification, which will void your processor warranty. Consult your motherboard manufacturer for compatibility.
Table 1. Intel® Chipsets Supporting Hyper-Threading Technology
Intel® Chipset | System Bus Support | Hyper-Threading |
955X | 1066, 800, 533 or 400 MHz | Yes |
945G/P | 1066, 800, 533 or 400 MHz | Yes |
925X | 1066, 800, 533 or 400 MHz | Yes |
915G/P | 800, 533 or 400 MHz | Yes |
875P | 800, 533 or 400 MHz | Yes |
865G | 800, 533 or 400 MHz | Yes |
865PE | 800, 533 or 400 MHz | Yes |
865P | 533 or 400 MHz | Yes |
850E | 533 or 400 MHz | Yes |
845E | 533 or 400 MHz | Yes |
845G (B-step only) | 533 or 400 MHz | Yes |
845GE | 533 or 400 MHz | Yes |
845PE | 533 or 400 MHz | Yes |
845GV | 533 or 400 MHz | Yes |
Motherboards must meet the electrical and mechanical specifications of the Intel processor, as documented in the Datasheet. Intel tests motherboards for based compatibility and lists passing boards on the Tested Motherboard List for specific Boxed Intel Processors.
It is important to verify that the specific motherboard model and revision support the specific boxed Intel processor speed being used. A BIOS upgrade may be required in order to properly recognize and initialize the latest stepping of the processor. The BIOS must also incorporate procedures or enhancements to enable multi-threading capability, for Intel processors supporting Hyper-Threading Technology. A BIOS upgrade may also be required in order to ensure support for Hyper-Threading Technology. See Hyper-Threading Technology Setup and Integration, for information on how to enable Hyper-Threading Technology for the system in BIOS settings.
Operating System Support
Intel recommends Hyper-Threading Technology for systems with Microsoft* Windows* XP Professional and Home versions or certain versions of Linux. These operating systems support and have optimizations for Hyper-Threading Technology. Service Pack 1 (or higher) for Windows XP must be installed to ensure full support for Hyper-Threading Technology. Certain versions of Linux will need to be updated (with available patches), in order to ensure support for Hyper-Threading Technology.
Other operating systems such as Microsoft Windows 95, Windows 98, Windows 98 SE, Windows NT 4, Windows 2000, Windows ME, and OS/2* do not support Hyper-Threading Technology for Intel processor-based systems. When using any of these operating systems, Hyper-Threading Technology must be disabled in the BIOS settings to ensure proper compatibility with the Intel processor (See Hyper-Threading Technology Setup and Integration). For Intel® Desktop Boards, Hyper-Threading Technology is enabled in the BIOS settings by default. Ensure you check the BIOS default setting prior to installation of the operating system.
Hyper-Threading Technology Branding Tool
Intel provides a software tool for system integrators to use for displaying the Intel® Pentium® 4 Processor with HT Technology2 logo. This software tool checks for the existence of supported platform components (See Platform Component Requirements) necessary to enable Hyper-Threading Technology functionality, before displaying the Intel Pentium 4 Processor with HT Technology logo (as a splash screen) during system startup. The splash screen is displayed for approximately 2 seconds after the operating system loads. System integrators should download and run this tool to help provide their customers visual assurance that the system meets the requirements of Hyper-Threading Technology for Pentium 4 processor-based systems.
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Section Contents Hyper-Threading Technology Setup and Integration > Enable Hyper-Threading Technology in BIOS Settings > Install Latest Service Pack or Patch >
When integrating a Pentium 4 processor-based system supporting Hyper-Threading Technology, it is important to ensure all platform component requirements are met.
Intel recommends the following integration sequence to effectively enable Hyper-Threading Technology:
- Enable Hyper-Threading Technology in BIOS Settings
- Install Operating System
- Install Latest Service Pack or Patch
- Install Intel INF Installation Utility
- Install latest Drivers
The recommended installation order is to ensure the optimal compatibility, functionality, and performance for Pentium 4 processor-based systems supporting Hyper-Threading Technology.
Enable Hyper-Threading Technology in BIOS Settings
Ensure you check the BIOS default setting prior to installation of the operating system. For your specific motherboard, ensure the switch to enable or disable Hyper-Threading Technology in BIOS settings is configured properly for Hyper-Threading Technology support. If the BIOS does not support Hyper-Threading Technology and a Pentium 4 Processor supporting Hyper-Threading Technology is installed in the motherboard, the switch to enable or disable Hyper-Threading Technology may not be present. Ensure that the latest BIOS is installed and supports Hyper-Threading Technology. Then, enter BIOS settings and configure the switch to turn-on the Hyper-Threading Technology feature.
Figure 4. Enabling hyper-threading technology in BIOS settings for Intel® desktop boards
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For Intel® Desktop Boards which support Hyper-Threading Technology, Hyper-Threading Technology will be enabled in the BIOS settings by default. To check that Hyper-Threading Technology is enabled for Intel Desktop Boards, enter BIOS settings and select "Enabled" under the Hyper-Threading Technology selection (See Figure 4). If the BIOS supports Hyper-Threading Technology and a Pentium 4 Processor 2.80 GHz (or below) without Hyper-Threading Technology is installed in a Intel Desktop Board, the Hyper-Threading Technology switch will be "grayed-out" and is disabled by default.
Install Operating System
Windows XP (Professional and Home versions) or certain versions of Linux are required for systems based on the Pentium 4 processor supporting Hyper-Threading Technology.
Install Latest Service Pack or Patch
System integrators should verify that the operating system they have selected supports the Pentium 4 processor supporting Hyper-Threading Technology. Latest service packs and patches must be installed to ensure best support for Hyper-Threading Technology. For Windows XP, install Service Pack 1 (available at http://www.microsoft.com/downloads). Certain versions of Linux will need to be updated (with available patches), in order to ensure support for Hyper-Threading Technology. See your operating systems vendor's website for the latest service packs and patches.
Install Intel INF Installation Utility
As with all of the new Intel chipsets, there are several resources in the Intel chipsets that are not automatically recognized by some Microsoft Windows operating systems. It is critical that the INF utility is installed in order to optimize platform performance with Intel Pentium 4 processor-based systems using Microsoft Windows XP. It is also critical that the INF utility is installed first before any other drivers.
Install Latest Drivers
Updated drivers may include compatibility fixes and/or optimizations for Hyper-Threading Technology. Download and install the latest drives from the vendor's website.
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Section Contents Verifying Hyper-Threading Technology in Windows* XP > Verifying Hyper-Threading Technology using Windows XP's Task Manager >
Determine whether Hyper-Threading Technology is enabled in Windows XP by viewing the Task Manager's CPU history graph or Device Manager.
Verifying Hyper-Threading Technology using Windows XP's Task Manager
Hyper-Threading Technology is enabled if there are two CPU usage history graphs within Windows XP Task Manager. If only one CPU graph is displayed and Hyper-Threading Technology is enabled in the BIOS settings, then make sure Microsoft Windows XP Service Pack 1 (or higher) is properly installed. Only one CPU history graph will be displayed in Task Manager if Hyper-Threading Technology is disabled in the BIOS settings.
Follow these steps, to verify Hyper-Threading Technology is enabled in Windows XP Task Manager:
- Right click Task Bar
- Click Task Manager
- Click the Performance tab
| Figure 5. Verifying hyper-threading technology in Windows* XP task manager Larger View > | Figure 6. Verifying hyper-threading technology in Windows* XP Device Manager Larger View > |
Hyper-Threading Technology is enabled if there are two processor listed in Windows XP Device Manager. Only one processor driver will be installed if Hyper-Threading Technology is disabled in the BIOS settings. Note: It is important to have the latest INF utility in order to optimize platform performance with Intel Pentium 4 processor-based systems using Microsoft Windows XP.
Follow these steps, to verify Hyper-Threading Technology is enabled in Windows XP Device Manager:
- Click Start Menu
- Click Control Panel
- Double click System
- Click the Hardware tab
- Click Device Manager
- Double click Processors
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Software Considerations
Existing software developed for Intel processors will run on Intel processors supporting Hyper-Threading Technology. Although existing applications will run correctly on the Intel processor supporting Hyper-Threading Technology, some applications may require simple code modifications which are recommended to get the optimum benefit from Hyper-Threading Technology. System integrators should verify the software they have selected is the latest version and whether it contains optimizations for Intel processors supporting Hyper-Threading Technology.
Applications optimized with multi-threaded code will show greatest performance benefits on Intel processor-based systems supporting Hyper-Threading Technology. In addition, the Intel processor supporting Hyper-Threading Technology will also see performance improvement in multi-tasking environments (running concurrent applications). Hyper-Threading Technology can improve the multi-tasking environment by reducing response time and run concurrent programs more efficiently. System integrators should contact software vendors to verify support and determine version information. More performance information for the Intel processor supporting Hyper-Threading Technology and Software Evaluation Guides are available on the http://www.intel.com/performance website.
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Additional Information
For additional technical details on Hyper-Threading Technology, refer to the following web sites:
- Hyper-Threading Technology Home Page, for white papers and presentations: http://www.intel.com/technology/platform-technology/hyper-threading/
- IA-32 Intel® Architecture Software Developer's Manuals: http://developer.intel.com/design/Pentium4/manuals/
- Software Technologies, Hyper-Threading Technology: http://softwarecommunity.intel.com/isn/home/default.aspx
More information on the Intel® Pentium® 4 processor is available on the Intel web.
1 Hyper-Threading Technology requires a computer system with an Intel® processor supporting HT Technology and Hyper-Threading Technology enabled chipset, BIOS and operating system. that utilize this technology, and an operating system that includes optimizations for this technology. Performance will vary depending on the specific hardware and software you use. See http://www.intel.com/products/ht/hyperthreading_more.htm for more information including details on which processors support HT Technology.
2 Look for systems with the Intel® Pentium® 4 processor with HT Technology logo which your system vendor has verified utilize Hyper-Threading Technology. Performance will vary depending on the specific hardware and software you use. See http://www.intel.com/products/ht/hyperthreading_more.htm for information.
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