Upper Memory Area (UMA) RAM

What is Upper Memory Area?

In computer architecture, the Upper Memory Area refers to the region between the conventional memory space and the High Memory Area which is usually set aside for the video memory and other peripherals.

From a technical point of view, the Upper Memory Area signifies the space in the memory architecture between 640 KB and 1024 KB (1 MB). This specific region is typically broken and made up of Upper Memory Blocks (UMBs).

Understanding Upper Memory Area

Understanding Upper Memory Area

The Upper Memory Area is a specific portion in the memory architecture represented as (0xA0000–0xFFFFF).

The area was used initially by the system devices such as the video display. However, in a Windows 9x computer, this area is used for specific purposes such as:

When you use the Upper Memory Area for either of the two purposes or both, you will have to load and use specific drivers such as EMM386.exe and HIMEM.SYS.

This is because the high memory typically attempts to get access to the Upper Memory Area.

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However, in the IBM architecture, the uppermost 384 KB of the 1024 KB address space reserved for use by different devices and peripherals, such as:

It was also used by the ROM BASIC, but the device is now obsolete.

Even after being used by so many peripherals, most of the 384 KB area was left unused. This added to the difficulty to the memory restriction of 640 KB even more.

Therefore, novel ways were used to fill up the empty spaces within the Random Access Memory (RAM). These specific areas were later referred to as the Upper Memory Blocks (UMBs).


Usually, in a DOS-based system, the memory is divided into five major areas, such as:

The Upper Memory Area is made up of Upper Memory Blocks (UMBs) and it can be accessed by using a special memory manager such as EMM386.exe.

Typically, in the earlier days when DOS was prevalent and systems had limited memory, users used to run larger applications that consumed almost the entire 640 KB area.

Different memory managers were available and used then to load and organize the Terminate-and-Stay-Resident (TSR) programs and drivers in the empty Upper Memory Area.

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EMM386 is one such software that was used extensively in Windows 3.0 and DOS 5.


The Upper Memory Area can be implemented in different ways in different systems. For example:


The Upper Memory Area contains different peripherals at different locations such as:

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The relevance and need for the Upper Memory Area increased with the gain in popularity of Windows 3.0. It helps in removing the 640 KB barrier.

However, the use of this specific area is different from the Upper Memory Blocks and needs specific memory managers to ensure that the addressable memory is left intact.