Expanded Memory

Definition of Expanded Memory

Expanded Memory, also known as Expanded Memory Specification (EMS), is a technology developed for older DOS-based computers to overcome the 640KB conventional memory limit. It utilizes a hardware or software interface to manage additional memory and divide it into 16KB pages, making it accessible for various applications. Expanded Memory became less relevant with the introduction of more advanced memory management systems in later operating systems.


The phonetics of the keyword “Expanded Memory” can be represented as:Expanded: ɪkˈspændɪdMemory: ˈmɛməriPut together, it would be: ɪkˈspændɪd ˈmɛməri

Key Takeaways

  1. Expanded Memory is a system that allows computers to access more memory than their original system limitations by utilizing an Expanded Memory Specification (EMS).
  2. It was primarily used in MS-DOS and early Windows operating systems to overcome the 640KB conventional memory limit for applications and services.
  3. Expanded Memory is now considered obsolete as modern systems can handle significantly larger amounts of memory natively, without needing any specialized memory management techniques.

Importance of Expanded Memory

The term “Expanded Memory” is important in the context of technology, as it refers to a memory management technique utilized in early IBM PC compatible computers, specifically those with Intel 80286 and the later x86 processors.

It was implemented through the Expanded Memory Specification (EMS) that enabled systems to surpass the conventional memory limit of 640 KB, a constraint of the early DOS operating systems, thus allowing applications and users to access more memory.

This approach was vital for enhancing the performance and functionality of software, especially in gaming and advanced business applications, during that era.

Although modern computing systems have evolved beyond utilizing expanded memory, its historical significance and the foundations it laid in memory management techniques continue to be relevant.


Expanded Memory emerged as a valuable tool for early computer systems, particularly in the 1980s and 1990s, to address the limitations of conventional memory and allow users to access a larger pool of memory resources. Its primary purpose was to overcome the constraints dictated by the 640KB memory barrier present in the original IBM PC architecture.

As new software applications and games demanded increased memory capacities to store and run their programs smoothly, expanded memory provided an effective solution by allocating memory beyond the conventional 1MB barrier so applications could access additional data without compromising the system’s performance. This additional memory, known as Expanded Memory, was utilized through a system called Expanded Memory Specification (EMS). EMS functioned by breaking up the extended memory into smaller, more manageable chunks called pages.

These pages were then swapped in and out of the available address space as needed by the programs running on the computer. This “paging” system enabled the applications to make the most of the limited address space, leading to improved overall performance and enhanced capabilities.

Furthermore, since many software applications and popular games at the time were designed to work specifically with EMS, Expanded Memory became a critical technological component for millions of personal computer users worldwide.

Examples of Expanded Memory

Expanded Memory refers to a memory management technique used in early personal computer systems, particularly the IBM PC and compatible models, to increase the amount of RAM available beyond the initial 1MB limitation imposed by the Intel 8086/8088 processors. This technology is also known as EMS (Expanded Memory Specification). Here are three real-world examples of Expanded Memory:

Lotus 1-2-3: In the late 1980s and early 1990s, the popular spreadsheet software Lotus 1-2-3 could take advantage of EMS to handle larger worksheets and perform more complex calculations. This was particularly useful for businesses that had large amounts of data to process, as the software could utilize expanded memory to break through the 640KB conventional memory limit on DOS-based systems.

AutoCAD: The early versions of AutoCAD, a computer-aided design (CAD) software, also benefited from expanded memory. Using EMS, AutoCAD could allocate additional memory for processes such as rendering and manipulating large graphical drawings. This allowed architects, engineers, and designers to work on more intricate projects and increase the overall efficiency of their work.

DOS-Based Gaming: EMS was widely used in DOS-based gaming in the late 1980s to mid-1990s, as games that required advanced graphics or extensive memory resources could take advantage of the extra memory. Popular titles such as Wing Commander and Ultima VII utilized expanded memory to load larger game levels, offer enhanced graphics, and deliver a smoother gaming experience.

Expanded Memory FAQ

1. What is Expanded Memory?

Expanded Memory is a technique used in earlier computer systems to increase the available memory beyond the conventional memory limit. This was done through the use of additional hardware or software, expanding the memory resources by allowing access to memory found in extended memory or on memory boards.

2. Why was Expanded Memory needed?

During the period of early computers, memory was a scarce and expensive component. Expanded Memory was needed because older computer systems, such as the IBM PC and its clones, could only address a limited amount of memory. Expanded Memory provided a means of utilizing more memory which allowed users to run larger programs and more demanding applications.

3. How did Expanded Memory work?

Expanded Memory worked by creating a “virtual” memory space using a combination of hardware and software. The memory manager would swap data between the limited conventional memory and the expanded memory, allowing users to access more memory than was available in the system’s physical memory space.

4. What is the difference between Expanded Memory and Extended Memory?

Expanded Memory is a technique used to increase the available memory beyond the conventional memory limit, while Extended Memory refers to the additional memory space available on IBM PC and compatible computers that use the Intel 80286 or higher processors. Extended Memory is directly accessible to the processor, whereas Expanded Memory is accessed through complex memory management arrangements.

5. Is Expanded Memory still relevant today?

Expanded Memory is generally not relevant in modern computer systems, as technological advancements have significantly increased the amount of memory available and provided more efficient memory management techniques. Most current operating systems efficiently manage memory, automatically allocating it to applications as needed, without the need for the user to manage the process.

Related Technology Terms

  • Extended Memory
  • Memory Management
  • EMS (Expanded Memory Specification)
  • Upper Memory Blocks (UMBs)
  • DOS Protected Mode Interface (DPMI)

Sources for More Information

Technology Glossary

Table of Contents

More Terms