Memory Type Range Register


Memory Type Range Register (MTRR) is a feature in modern x86 processors that provides a mechanism to control and optimize memory caching. MTRRs allow the CPU to efficiently access specific memory address ranges by assigning different cache attributes, such as write-back or uncachable, to these ranges. This enhances the overall system performance and prevents conflicts between memory devices, especially in regard to video memory.

Key Takeaways

  1. Memory Type Range Registers (MTRRs) are a set of processor registers that allow developers to control and optimize how the CPU caches memory, improving system performance.
  2. MTRRs are mainly used to manage the Write-Combining (WC) and Write-Protect (WP) memory types, enabling efficient manipulation and data transfer in video and graphics applications.
  3. These registers are crucial for optimizing memory access, but improper use can lead to system instability. Advanced developers and operating systems typically manage MTRRs to avoid conflicts and maximize performance.


Memory Type Range Registers (MTRRs) are important in computer systems because they allow the CPU to efficiently handle memory access by controlling the caching mechanism for different types of memory ranges.

By optimizing how memory is cached, MTRRs enhance the overall performance and functionality of the system.

They enable the CPU to assign specific cache settings for individual memory regions, such as write-back, write-through, or write-protect, depending on the nature and requirements of the device or data being handled.

Consequently, MTRRs play a crucial role in optimizing memory operations and ensuring stable and efficient system performance.


Memory Type Range Register (MTRR) is a crucial component in the optimization of system performance, particularly in enhancing how a computer’s central processing unit (CPU) interacts with the memory system. MTRRs are utilized to control caching techniques in the memory subsystem, ensuring the CPU can access memory locations rapidly and efficiently. This is achieved by providing a way to assign distinct caching policies or memory types to particular regions within the physical address space.

As a result, the CPU can make informed decisions about how to access various types of memory, whether it be random access memory (RAM) or other memory regions, leading to substantial speed improvements for the entire system. MTRRs enable the configuration of caching behavior to be tailored to the performance characteristics of specific hardware or the requirements of specific applications. Some of the memory types supported by MTRRs include write-protected, write-combining, write-through, and write-back.

These memory types offer a balance between performance and data protection based on the read and write patterns of the application, the type of memory being accessed, and the overall system architecture. For example, MTRRs can be used to ensure that memory-mapped I/O devices are properly flagged as uncachable. This prevents the CPU cache from storing inaccurate copies of the device’s state, leading to potential system instability.

Overall, the Memory Type Range Register plays a vital role in improving system performance and ensuring efficient and reliable communication between the CPU and memory subsystems.

Examples of Memory Type Range Register

Memory Type Range Register (MTRR) is a feature found in the x86 architecture of processors. It is designed to improve performance and efficiency by controlling how the CPU caches different memory regions. Here are three real-world examples of applications that benefit from MTRR optimizations:

Graphic-intensive Applications: Applications that utilize graphics heavy computations, such as video games and 3D modeling software, rely on fast access to both system and video memory. Optimized MTRR settings enhance system performance by efficiently caching framebuffer memory to reduce memory access latency. This can lead to smoother gameplay or renderings in these applications.

Video Playback and Streaming: Video playback and streaming applications like VLC, YouTube, and Netflix benefit from optimized MTRR settings by improving the speed of accessing video frames from memory during decoding and displaying. This helps minimize stuttering or lagging in video playback and maintains a smooth visual experience for the end user.

High-performance Computing (HPC): MTRR optimizations can be essential in scientific research, data analysis, and simulations that require high-performance computing. MTRR optimizations ensure that various memory regions, such as main memory, high-bandwidth memory, and device memory, are cached effectively, leading to faster computation and data transfer speeds.

Memory Type Range Register FAQ

What is a Memory Type Range Register (MTRR)?

A Memory Type Range Register (MTRR) is a processor feature that enables more efficient handling of memory operations for modern CPUs. MTRRs allow the CPU to assign different caching policies to specific memory address ranges, thereby improving performance for memory-intensive tasks.

How do MTRRs benefit system performance?

MTRRs benefit system performance by allowing a CPU to optimize memory access with specific caching policies for different memory types. Some memory ranges can be set to write-through, write-combining, write-protect, or uncachable, improving overall performance and reducing latency for certain applications.

What are the common MTRR types?

There are five common types of MTRRs: Uncachable (UC), Write-Combining (WC), Write-Through (WT), Write-Protect (WP), and Write-Back (WB). Each type has a specific cache policy designed to optimize memory operations dependent on the characteristics of the memory range being accessed.

How can I configure MTRRs on my system?

MTRRs are typically configured by the system BIOS or operating system. On some systems, it may be possible to manually configure MTRRs through BIOS settings, but doing so incorrectly could negatively impact system performance. It is usually recommended to allow your system to handle MTRR configuration automatically.

How do I check my system’s MTRR settings?

To check your system’s MTRR settings, you can use specific tools depending on your operating system. For Windows, you can use a tool like CPU-Z to view current MTRR settings. For Linux, the “cat /proc/mtrr” command in the terminal will display the current MTRR configuration.

Related Technology Terms

  • Address Space
  • Cache Memory
  • Memory Controller
  • Memory Mapping
  • Memory Protection

Sources for More Information

  • Intel Corporation – As the creator of the Memory Type Range Registers, Intel’s official website offers reliable information on MTRRs and their functionalities.
  • AMD – As one of the major manufacturers of processors, AMD’s official website provides information on MTRRs from their perspective, with a focus on compatibility and implementation in AMD processors.
  • Wikipedia – As a widely-used, community-driven encyclopedia, Wikipedia features an in-depth article on Memory Type Range Registers, including their purpose, usage, and history.
  • – This community-driven website is dedicated to providing resources for operating system design and development. It contains an informative article about MTRRs and how to work with them in custom-built operating systems.

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