UPER MEMORY AREA (UMA)
The term Uper Memory Area (UMA ) describe the reserved 384K at the top of the first megabyte of system memory on a PC/XT and the the first megabyte on a AT-type system. This memory has the address from A0000 through FFFFF.
The first 128k after conventional memory is called video RAM. It is reserved for use by video adapter. When text and graphics are displayed on-screen, the elecronics impulses that contain their images. reside in this space. Video RAM is allotted the address range from A0000-BFFFF.
The next 128K is reserved for the adapter BIOS that reside in read-only memory chips on some adapter board plugged into the bus slot. Most VGA-compatible video adapter use the first 32K of this area for their on-board BIOS, The rest can be used by any other adapters installed. Many network adapter also use this area for speacial purpose RAM called Shared Memory. Adapter ROM and special purpose RAM is allotted the address range from C0000-DFFFF.
The last 128K of memory is reserved for mother board BIOS, Whisch is stored in red-only RAM chips or ROM. The POST - Power-on self test and bootstratp loader, which handles your system at bootup until the operating system takes over, alsoreside in this space. MOST systems only use the last 64K of this space, leaving the first 64K or more free for re-mapping with memory managers. Some system also include the CMOS Setu program in this area. The motherboard BIOS is allotted the range from EOOOO-FFFFF
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