Term of the Moment
computer
Redirected from: upper memory
Definition: UMA
(1) (Unlicensed Mobile Access) See GAN.
(2) (Upper Memory Area) Memory between 640K and 1M in an early PC. The UMA was broken into upper memory blocks (UMBs) reserved for the screen and other peripherals. In the days of DOS and limited memory, people wanted to run larger applications that took up much of the lower 640K. A variety of different memory managers became available to load and manage drivers and TSRs into unoccupied UMA blocks. EMM386, which came with DOS 5 and Windows 3.0, was an example. See PC I/O addressing, EMM386.EXE and QEMM.
Memory in Early PCs
(2) (Upper Memory Area) Memory between 640K and 1M in an early PC. The UMA was broken into upper memory blocks (UMBs) reserved for the screen and other peripherals. In the days of DOS and limited memory, people wanted to run larger applications that took up much of the lower 640K. A variety of different memory managers became available to load and manage drivers and TSRs into unoccupied UMA blocks. EMM386, which came with DOS 5 and Windows 3.0, was an example. See PC I/O addressing, EMM386.EXE and QEMM.
Memory was precious in early PCs. For example, the first IBM PC in 1981 had 16KB to 256KB, and 640KB was a top limit for all PCs for a while. Today's computers are no comparison; for example, Apple's Mac Pro can have 300,000 times as much RAM. Following is the allocation of the first megabyte of memory in an early PC.