In DOS memory management, the upper memory area (UMA) refers to memory between the addresses of 640 KB and 1024 KB (0xA0000–0xFFFFF) in an IBM PC or compatible. IBM reserved the uppermost 384 KB of the 8088 CPU's 1024 KB address space for ROM, RAM on peripherals, and memory-mapped input/output. For example, the monochrome video memory area runs from 704 to 736 KB (0xB0000–B7FFF).
However, even with video RAM, the ROM BIOS and I/O ports for expansion cards, much of this 384 KB of address space was unused. As the 640 KB memory restriction became ever more of an obstacle, techniques were found to fill the empty areas with RAM. These areas were referred to as upper memory blocks (UMBs).
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Famous quotes containing the words upper, memory and/or area:
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Would sing her song and dance her turn, now here
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—William Shakespeare (1564–1616)
“All vital truth contains the memory of all that for which it is not true.”
—D.H. (David Herbert)
“If you meet a sectary, or a hostile partisan, never recognize the dividing lines; but meet on what common ground remains,—if only that the sun shines, and the rain rains for both; the area will widen very fast, and ere you know it the boundary mountains, on which the eye had fastened, have melted into air.”
—Ralph Waldo Emerson (1803–1882)