Processors
Intel® Pentium® 4 Processors
Integration Overview for Systems Based on the Intel® Pentium® 4 Processor

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 technical information specific to Intel Pentium 4 processors supporting Intel® HT Technology and is intended to aid in system integration.

Note Before building a Intel Pentium 4 Processor-based system, consult the motherboard manual, boxed processor manual, and the integration overview for systems based on the Intel Pentium 4 Processor in the 478-pin Package (the following information is intended to be supplementary to these documents).
Intel® Hyper-Threading Technology (Intel® HT Technology) overview
Intel brings the advancement of Intel® HT Technology to the desktop computing platform. This new technology, coupled with the existing Intel NetBurst® microarchitecture, is designed to deliver superior performance for even the most demanding applications and environments. The Intel Pentium 4 Processor brand name reflects breakthrough technology and performance that combines innovative new features with proven Intel quality.

Intel® HT 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 Pentium 4 Processor supporting Intel HT 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 Intel Pentium 4 Processor core.

Comparison of a Intel Pentium 4 Processor Supporting Intel HT Technology and a traditional dual processor system
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 a intel Pentium 4 Processor supporting Intel® Hyper-Threading Technology (Intel® HT Technology) share the execution resources of the processor core (see Figure 2), which include the execution engine, caches, system bus interface, and the firmware. Intel HT Technology is designed to improve the performance of Pentium 4 processors by maximizing the use of available execution resources in the Intel NetBurst® microarchitecture, and exploiting the multi-threaded nature of contemporary operating systems.

Intel NetBurst® microarchitecture Duplicated and Shared Resources for Intel Pentium 4 Processors Supporting Intel HT Technology
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. The same division of workload can be found in many multi-threaded applications. 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 to keep as many of its execution units as possible busy during each clock cycle. Multi-tasking environments can 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 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 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 a 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 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 3C shows the result of system based on the Pentium 4 processor supporting Intel HT Technology. This configuration allows the Pentium 4 processor supporting Intel HT 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 Pentium 4 processor supporting Intel HT Technology is utilizing the execution units more frequently and reducing idle time on the processor. Resource utilization can increase significantly for the Pentium 4 processor supporting Intel HT 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. Pentium 4 processors supporting Intel HT 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.

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
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

Note This figure is a demonstration of the concepts underlying Intel® Hyper-Threading Technology (Intel® HT Technology) and does not attempt to show the resource utilization patterns of any existing processors or software application.


Platform component requirements
Enabling Intel HT Technology on a 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
The above requirements are specific to integrating Pentium 4 processor-based systems supporting Intel HT Technology.

Note Before building a Pentium 4 processor-based system, consult the motherboard manual, boxed processor manual, and the Integration Overview for Systems Based on the Pentium 4 Processor in the 478-pin Package or the Integration Overview for Systems Based on the Pentium 4 processor in the 775-land package (the following information is intended to be supplementary to these documents).

Processor selection
Intel® Pentium® 4 Processors supporting Intel® Hyper-Threading Technology (Intel® HT Technology) also support the 533 MHz and 800 MHz system bus (Not all 533MHz system bus processors support Intel HT Technology).

Motherboard selection
Motherboards used with the Pentium 4 processor supporting Intel HT Technology must utilize a chipset which supports the Intel NetBurst Microarchitecture and Intel HT Technology. Table 1 shows a listing of Intel® chipsets that support the Intel NetBurst microarchitecture and Intel HT 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 Intel HT Technology

Intel Chipset System Bus Support Intel HT Technology
Support
 

1066, 800, or 533 MHz

1066, 800, or 533 MHz

Yes

Yes

945P

1066, 800, or 533 MHz

Yes

925XE 1066 MHz Yes
925X 800 Yes
915P 800 or 533 MHz Yes
915G 800 or 533 MHz Yes

910GL

533 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® Pentium® 4 Processor, as documented in the Datasheet. Also, the Intel Pentium 4 Processor in the 478-pin package must be used in a motherboard with a 478-pin micro-PGA (mPGA478B) socket.

It is important to verify that the specific motherboard model and revision support the specific Pentium 4 processor speed being used. A BIOS upgrade may be required in order to properly recognize and initialize the latest stepping of the Pentium 4 processor. The BIOS must also incorporate procedures or enhancements to enable multi-threading capability, for 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
The following operating systems are not recommended for use with Intel HT Technology. If you are using one of the following operating systems, it is advised that you should disable Intel HT Technology in the system BIOS Setup program:
  • 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® Hyper-Threading Technology (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 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 includes the necessary system ingredients for Intel® HT Technology 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, it is important to ensure all platform component requirements are met.

Intel recommends the following integration sequence to effectively enable Intel HT Technology:
  1. Enable Intel HT Technology in BIOS settings
  2. Install operating system
  3. Install latest service pack or patch
  4. Install Intel INF Installation Utility
  5. Install latest drivers
The recommended installation order is to ensure the optimal compatibility, functionality and performance for Pentium 4 processor-based systems supporting Intel HT Technology.

Enable Intel HT 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 Intel HT Technology in BIOS settings is configured properly for Intel HT Technology support. If the BIOS does not support Intel HT Technology and a Intel Pentium 4 Processor supporting Intel HT Technology is installed in the motherboard, the switch to enable or disable Intel HT Technology may not be present. Ensure that the latest BIOS is installed and supports Intel HT Technology, and then enter the BIOS settings and configure the switch to turn-on the Intel HT Technology feature.

For Intel® Desktop Boards that support Intel HT Technology, Intel HT Technology will be enabled in the BIOS settings by default. To check that Intel HT Technology is enabled for Intel Desktop Boards, 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 an Intel Desktop Board, the Intel HT Technology switch will be "grayed-out" and is disabled by default.

Enabling Hyper-Threading Technology in BIOS settings for Intel® Desktop Boards
Figure 4. Enabling Intel HT Technology in BIOS settings for Intel® Desktop Boards

Install operating system
Install the operating system.

Install latest service pack or patch
Intel recommends using Service Pack 1 (SP1) with Windows XP* Home or XP Professional. It is always good practice to use the most current version of the operating system. In addition, 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. Windows XP Service Pack 1 is available at http://www.microsoft.com/en-us/download/default.aspx*.

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 Intel HT Technology. Download and install the latest drives from the vendor's Web site.

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.

Follow these steps, to verify Intel HT Technology is enabled in Windows XP Task Manager:

  1. Right click Task Bar
  2. Click Task Manager
  3. Click the Performance tab
Verifying Hyper-Threading Technology in Windows* XP task manager
Figure 5. Verifying Intel HT Technology in Windows XP task manager

Verifying Intel HT Technology in Windows* XP Task 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.
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 Intel HT Technology is enabled in Windows XP Device Manager:

  1. Click Start Menu.
  2. Click Control Panel.
  3. Double click System.
  4. Click the Hardware tab.
  5. Click Device Manager.
  6. Double click Processors.
Verifying Hyper-Threading Technology in Windows* XP device manager
Figure 6. Verifying Intel HT Technology in Windows* XP device manager

Software Considerations
Existing software developed for Intel® processors will run on Intel Pentium 4 Processors supporting Intel HT Technology. Although existing applications will run correctly on the Pentium 4 processor supporting Intel HT Technology, some applications may require simple code modifications which are recommended to get the optimum benefit from Intel HT Technology. System integrators should verify the software they have selected is the latest version and whether it contains optimizations for Pentium 4 processors supporting Intel HT Technology.

Applications optimized with multi-threaded code will show greatest performance benefits on a Pentium 4 processors-based systems supporting Intel HT Technology. In addition, the Pentium 4 processor supporting Intel HT Technology will also see performance improvement in multi-tasking environments (running concurrent applications). Intel HT 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 Pentium 4 processor supporting Intel HT Technology and Software Evaluation Guides are available on the http://www.intel.com/performance web site.

Additional Information
For additional technical details on Intel HT Technology, refer to the following Web sites:
  • Intel HT Technology Home Page
  • More information on the Intel Pentium 4 Processor is available on the Intel Web site.

    Intel HT Technology requires a computer system with an Intel Pentium 4 Processor supporting Intel HT Technology and a Intel HT Technology enabled chipset, BIOS and operating system. Performance will vary depending on the specific hardware and software you use.

This applies to:

Intel® Pentium® 4 Processors



Solution ID: CS-017371
Last Modified: 23-Oct-2014
Date Created: 23-Nov-2004
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