The following overview and integration instructions are for professional system integrators building PCs that use Intel® Pentium® 4 Processors supporting Intel® Hyper-Threading Technology (Intel® HT Technology) with industry-accepted motherboards and peripherals. It contains specific technical information and intends to aid in system integration.
- Platform component requirements
- Intel HT Technology Setup and Integration
- Verifying Intel HT Technology in Windows XP*
- Software Considerations
- Additional Information
Intel® Hyper-Threading Technology (Intel® HT Technology) overview
Intel brings the advancement of Intel® HT Technology to the desktop computing platform. Intel® HT Technology, coupled with the existing Intel NetBurst® microarchitecture, is designed to deliver superior performance for even the most demanding applications and environments. It enables a single physical processor to execute two separate code streams (called threads) concurrently, increasing processor utilization and providing greater throughput and improved performance.
The Intel® Pentium® 4 Processor reflects breakthrough technology and performance that combines innovative new features with proven Intel quality. The Intel® Pentium® 4 Processor supporting Intel® HT Technology consists of two logical processors (see Figure 1). Each has its own architectural state. The architectural state duplicated for each logical processor consists of data registers, segment registers, control registers, debug registers, and most MSRs or Model Specific Registers. Each logical processor also has its own Advanced Programmable Interrupt Controller (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 Intel® Pentium® 4 Processor core.
Figure 1. Comparison of a Intel® Pentium® 4 Processor Supporting Intel® HT 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® Pentium® 4 Processor supporting Intel® HT Technology share the execution resources of the processor core (see Figure 2). Execution resources include execution engine, caches, system bus interface, and firmware.
Intel® HT Technology improves the performance of Intel® Pentium® 4 Processors by maximizing the use of available execution resources in the Intel NetBurst® Microarchitecture and by exploiting the multi-threaded nature of contemporary operating systems.
Figure 2. Intel NetBurst® microarchitecture Duplicated and Shared Resources for Intel® Pentium® 4 Processors Supporting Intel HT Technology
Most contemporary operating systems (including Microsoft Windows XP* and Linux*) divide their workload into processes and threads that can be independently scheduled and dispatched to run on two or more processors. Many multi-threaded applications divide workload. Intel® HT 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® Pentium® 4 Processor using out-of-order instruction scheduling. As many execution units as possible are kept busy during each clock cycle.
Multitasking environments also benefit from Intel® Hyper-Threading Technology (Intel® HT Technology). Concurrent applications can resemble multi-threaded application workloads to the processor, as each program issues an independent thread for execution. Intel® HT Technology increases processing efficiency, which gives you better responsiveness and immediate performance when running concurrent applications.
To understand how Intel® HT 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 an Intel® Pentium® 4 Processor supporting Intel® HT 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. The DP system contains two superscalar processors that can each execute up to three instructions every cycle and allow two separate threads to be executed ("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 used 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 3C shows the result of system based on the Intel® Pentium® 4 Processor supporting Intel® HT Technology. The configuration allows the 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® Pentium® 4 Processor supporting Intel® HT Technology uses execution units more frequently and reduces processor idle time. Resource utilization can increase significantly but is dependent on how each application is designed to use threading and resources with the processor. For example, if an application is multi-threaded by different threads using 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® Pentium® 4 Processors supporting Intel® HT Technology increase instruction processing throughput. They take advantage of otherwise idle processor resources, improving performance on both multi-threaded applications and multitasking environments.
Figure 3. Comparison of execution on a traditional single processor system, a traditional dual processor system, and a Intel® Pentium® 4 Processor-based system supporting Intel® HT Technology
Platform component requirements
Enabling Intel® HT Technology on an Intel® Pentium® 4 Processor-based system requires all of the following platform components:
- Intel® Pentium® 4 Processor supporting Intel® HT Technology
- A motherboard that supports Intel® HT Technology
- An operating system that includes optimizations for Intel® HT Technology
Motherboards used with the Intel® Pentium® 4 Processor supporting Intel® HT Technology must use a chipset that supports the Intel® NetBurst Microarchitecture and Intel® HT Technology. Table 1 shows a listing of supporting Intel® Chipsets.
Table 1. Intel® Chipsets Supporting Intel® HT Technology
Motherboards must meet the electrical and mechanical specifications of the Intel® Pentium® 4 Processor, as documented in the Datasheet. The Intel® Pentium® 4 Processor in the 478-pin package must be used in a motherboard with a 478-pin micro-PGA (mPGA478B) socket.
Verify that the specific motherboard model and revision support your specific Intel® Pentium® 4 Processor speed. A BIOS upgrade may be required in order to properly recognize and initialize the latest stepping of the Intel® Pentium® 4 Processor. The BIOS must also incorporate procedures or enhancements to enable multi-threading capability, for Intel® Pentium® 4 Processors supporting Intel® HT Technology. A BIOS upgrade may also be required in order to ensure support for Intel® HT Technology.
Operating System Support
Microsoft Windows* Operating System Based PCs
The following desktop operating systems include optimizations for HT Technology and are currently eligible to carry the new Intel® Pentium® 4 Processor with HT Technology logo:
- Microsoft Windows XP* Professional Edition
- Microsoft Windows XP* Home Edition
- Microsoft Windows 2000* (all versions)
- Microsoft Windows NT* 4.0
- Microsoft Windows Me*
- Microsoft Windows 98*
- Microsoft Windows 98 SE*
Linux* operating system desktop based PCs
The following Linux* operating systems include optimizations for Intel® HT Technology and are currently eligible to carry the Intel® Pentium® 4 Processor with Intel® HT Technology logo:
- Red Hat Linux* 9 (Professional and Personal versions)
- SuSE Linux* 8.2 (Professional and Personal versions)
- Red Flag Linux* Desktop 4.0
- COSIX* Linux* 4.0
Note that while other Linux* operating systems may have Intel® HT Technology enabled, only the distributions above are currently eligible to carry the Intel® Pentium® 4 Processor with HT Technology logo. If purchasing a PC based on a different Linux operating system, check with your PC vendor to determine if the PC meets necessary system requirements and has Intel® HT Technology enabled.
Intel® HT Technology setup and integration
When integrating a Intel® Pentium® 4 Processor-based system supporting Intel® HT Technology, ensure all platform component requirements are met. Intel recommends the following integration sequence to effectively enable Intel HT Technology. The integration sequence ensures optimal compatibility, functionality, and performance.
- Enable Intel® HT Technology in BIOS settings
- Install operating system
- Install latest service pack or patch
- Install Intel INF Installation Utility
- Install latest drivers
Enable Intel® HT Technology in BIOS Settings
Check the BIOS default setting before installing the operating system. For your specific motherboard, ensure the switch to enable or disable Intel® HT Technology in BIOS settings is configured properly. If the BIOS does not support Intel® HT Technology, and an Intel® Pentium® 4 Processor supporting Intel® HT Technology is installed in the motherboard, the switch may not be present. Ensure the latest BIOS is installed and supports Intel® HT Technology. Then enter the BIOS settings and configure the switch to turn-on the Intel® HT Technology feature.
For supporting Intel® Desktop Boards, Intel® HT Technology will be enabled in the BIOS settings by default. To check if Intel® HT Technology is enabled, enter BIOS settings and select "Enabled" under the Intel® HT Technology selection (See Figure 4). If the BIOS supports Intel® HT Technology and a Pentium® 4 Processor 2.80 GHz (or below) without Intel® HT Technology is installed in the desktop board, the switch will be "grayed-out" and is disabled by default.
Install latest service pack or patch
Intel recommends using Service Pack 1 (SP1) with Windows XP* Home or XP Professional. You should always use the most current operating system version. Additionally, Microsoft has incorporated several features in SP1 for Windows XP to address common application issues and improve compatibility with MP environments, including Intel® HT Technology.
Get the Windows XP Service Pack 1*.
Install Intel® INF Installation Utility
Some Windows* operating systems do not automatically recognize resources in Intel® Chipsets.
To optimize platform performance with Intel® Pentium® 4 Processor-based systems using Windows XP*, you MUST install the INF utility before any other drivers.
Install Latest Drivers
Updated drivers may include compatibility fixes and/or optimizations for Intel® HT Technology. Download and install the latest drives from the vendor's website.
Verifying Intel® HT Technology in Windows XP*
Determine whether Intel® HT Technology is enabled in Windows XP* by viewing the Task Manager's CPU history graph or Device Manager.
Verifying Intel® HT Technology using Windows XP's Task Manager*
Intel® HT Technology is enabled if there are two CPU usage history graphs within Windows XP Task Manager. If only one CPU graph is displayed and Intel HT 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 Intel HT Technology is disabled in the BIOS settings.
To verify Intel® HT Technology is enabled in Windows XP Task Manager:
- Right click Task Bar
- Click Task Manager
- Click the Performance tab
Figure 5. Verifying Intel® HT Technology in Windows XP Task Manager*
Verifying Intel® HT Technology in Windows* XP Device Manager
Intel® HT Technology is enabled if there are two processor listed in Windows XP Task Manager. Only one processor driver will be installed if Intel® HT Technology is disabled in the BIOS settings.
To verify Intel® HT 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.
Figure 6. Verifying Intel® HT Technology in Windows XP Device Manager*
Existing software developed for Intel® Processors will run on Intel® Pentium® 4 Processors supporting Intel® HT Technology. Although existing applications will run correctly, some applications may require simple code modifications. Modifications are recommended to get the optimum benefit from Intel® HT Technology. System integrators should verify the software selected is the latest version and whether it contains optimizations for Intel® Pentium® 4 Processors supporting Intel® HT Technology.
Applications optimized with multi-threaded code will show the greatest performance benefits. Intel® Pentium® 4 Processor supporting Intel® HT Technology will also see performance improvement in multitasking environments (running concurrent applications). Intel® HT Technology can improve the multitasking environment by reducing response time and running concurrent programs more efficiently.System integrators should contact software vendors to verify support and determine version information.
See performance information and Software Evaluation Guides for the Intel® Pentium® 4 Processor supporting Intel® HT Technology.
For additional technical details on Intel® HT Technology, see the following:
Intel® HT Technology requires a computer system with an Intel® Pentium® 4 Processor supporting Intel® HT Technology, and an Intel® HT Technology enabled chipset, BIOS and operating system. Performance will vary depending on the specific hardware and software you use.