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Upper memory area

In DOS memory management, the upper memory area (UMA) is the 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 BIOS ROM, Video BIOS, Option ROMs, video RAM, RAM on peripherals, memory-mapped I/O, and obsoleted ROM BASIC.

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Upper memory area

Nodes57
Edges56
Triples42
Avg. degree1.96
Density0.035088
Components1

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Upper memory area

Top relations

related to IBM XT · 16
Upper memory area → As, DOS, EFFFF, KB, Lotus, MB, On IBM XT, Programs, PROM, RAM, The AllCard, Therefore, This, TSR, TSRs, XT-class
related to Windows · 14
Upper memory area → Also, API, CD, DOS, DOS Protected Mode Interface, DPMI, However, Only, Specifically, The, VCPI, Virtual Control Program Interface, Windows, With
related to Virtual 8086 Mode · 5
Upper memory area → EMM386, Memory Specification, The, This, Upper

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Important terminology

memory kb upper dos ram programs area blocks 640 conventional address mode ibm umbs 384 rom emm386 could loaded drivers

Entity relationships Subject–Predicate–Object triples

SubjectPredicateObjectConfidenceSrc
MSCDEX could also be loaded into the UMA in a similar fashioninstance ofConventional memory glutton programs0.80text
hence freeing up a large amount of conventional memory.WindowsThe increasing popularity of Windows 3.0 made the necessity of the upper memory area less relevantinstance ofConventional memory glutton programs0.80text
as Windows applications were not directly affected by DOS' base memory limitsinstance ofConventional memory glutton programs0.80text
but DOS programs running under Windowsinstance ofConventional memory glutton programs0.80text
Lotus 1-2-3instance ofPrograms0.80text
which accessed video memory directlyinstance ofPrograms0.80text
needed to be patched to handle this memory layoutinstance ofPrograms0.80text
Upper memory arearelated to IBM XTOn IBM XT0.60section
Upper memory arearelated to IBM XTPROM0.60section
Upper memory arearelated to IBM XTAs0.60section
Upper memory arearelated to IBM XTRAM0.60section
Upper memory arearelated to IBM XTTSR0.60section

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