upper memory area

The command line argument allows the use of the upper memory area.

Loads program into upper memory area.

SYS device driver into the upper memory area.

EXE is , which allows use of the upper memory area without emulating expanded memory.

Upper memory blocks can be created by mapping extended memory into the upper memory area when running in virtual x86 mode.

It's a complex process, but if you really must have the maximum Upper memory area, then QEMM is still the one for you.

For more information on this, see the article on the Upper Memory Area (UMA).

Upper memory area (UMA)

Upper Memory Area (UMA)

Other components, such as device drivers and TSRs, could be loaded into the upper memory area (UMA).

Not all addresses in the upper memory area were used in a typical system; unused physical addresses would return undefined and system-dependent data if accessed by the processor.

In practice the upper memory area will be provided by the expanded memory manager (EMM), after which DOS will try to allocate them all and manage them itself.

Loadhigh (abbreviated 'lh') is an internal MS-DOS command that is used to load a program into the upper memory area (UMA) instead of conventional memory.

EXE can map memory into unused blocks in the upper memory area (UMA), allowing device drivers and TSRs to be "loaded high", preserving conventional memory.

These memory areas are referred to as the high memory area (HMA) and the upper memory area (UMA; also referred to as upper memory blocks or UMBs).

After completing the POST, the motherboard BIOS scans for extension ROMs in an area of the "upper memory area" space and runs each ROM found, in order.

The first was the Expanded Memory Specification (EMS) which originally allowed memory on an add-on card to be accessed via a 64 KB page frame in the reserved upper memory area.

On IBM XT computers, it was possible to add more memory to the motherboard and use a custom address decoder PROM to make it appear in the upper memory area [1].

The design of the original IBM PC placed the Color Graphics Adapter (CGA) memory map and other hardware in the 384 KB upper memory area (UMA).

Hardware expansion boards could use any of the upper memory area for ROM addressing, so the upper memory blocks were of variable size and in different locations for each computer, depending on the hardware installed.

Since an expansion card such as a video adapter, hard drive controller, or network adapter could use allocations of memory in many of the upper memory areas, configuration of some combinations of cards required careful reading of documentation, or experimentation, to find card settings and memory mappings that worked.

It is a form of bank switching technique that allows more than the 640 KB of RAM defined by the original IBM PC architecture, by letting it appear piecewise in a 64 KB "window" located in the Upper Memory Area.

The increasing popularity of Windows 3.0 made the necessity of the upper memory area less relevant, as Windows applications were not affected by DOS' base memory limits, but DOS programs running under Windows (with Windows itself acting as a multitasking manager) were still thus constrained.

This usage of the upper memory area is different from using upper memory blocks, which was used to free conventional memory by moving device drivers and TSRs into the upper 384 KB of the 1 MB address space, but left the amount of addressable memory (640 KB) intact.