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SYSTEM MEMORY MAP - OVERALL

 The IBM PC handles its address space in 64k segments, divided into 16k
 fractions and then further as necessary.

-----------------------------------------------------------------------------
start |start end  |
addr. |addr. addr.|                          usage
(dec) |   (hex)   |
-----------------------------------------------------------------------------
   *640k RAM Area*
-----------------------------------------------------------------------------
 0k   |           |  start of RAM
 16k  |00000-03FFF|  PC-0 system board RAM
 32k  |04000-07FFF|
 48k  |08000-0BFFF|
------+-----------+----------------------------------------------------------
 64k  |10000-13FFF|  PC-1 system board RAM
 80k  |14000-17FFF|
 96k  |18000-1BFFF|
 112k |1C000-1FFFF|
------+-----------+----------------------------------------------------------
 128k |20000-23FFF|
 144k |24000-27FFF|
 160k |28000-2BFFF|
 176k |2C000-2FFFF|
------+-----------+----------------------------------------------------------
 192k |30000-33FFF|
 208k |34000-37FFF|
 224k |38000-3BFFF|
 240k |3C000-3FFFF|
------+-----------+----------------------------------------------------------
 256k |40000-43FFF|  PC-2 system board RAM
 272k |44000-47FFF|
 288k |48000-4BFFF|
 304k |4C000-4FFFF|
------+-----------+----------------------------------------------------------
 320k |50000-53FFF|
 336k |54000-57FFF|
 352k |58000-5BFFF|
 368k |5C000-5FFFF|
------+-----------+----------------------------------------------------------
 384k |60000-63FFF|
 400k |64000-67FFF|
 416k |68000-6BFFF|
 432k |6C000-6FFFF|
------+-----------+----------------------------------------------------------
 448k |70000-73FFF|
 464k |74000-77FFF|
 480k |78000-7BFFF|
 496k |7C000-7FFFF|
------+-----------+----------------------------------------------------------
 512k |80000-83FFF|
 528k |84000-87FFF|
 544k |88000-8BFFF|  the original IBM PC-1 BIOS limited memory to 544k
 560k |8C000-8FFFF|
------+-----------+----------------------------------------------------------
 576k |90000-93FFF|
 592k |94000-97FFF|
 609k |98000-9BFFF|
 624k |9C000-9FFFF|  to 640k (top of RAM address space)
-----------------------------------------------------------------------------
A0000 ***** 64k ***** EGA address
-----------------------------------------------------------------------------
 640k |A0000-A95B0|  MCGA 320x200 256 color video buffer
      |     -AF8C0|  MCGA 640x480 2 color video buffer
      |     -A3FFF|
 656k |A4000-A7FFF|
 672k |A8000-ABFFF|      this 64k segment may be used for contiguous DOS
 688k |AC000-AFFFF|      RAM with appropriate hardware and software
-----------------------------------------------------------------------------
B0000 ***** 64k ***** mono and CGA address
-----------------------------------------------------------------------------
 704k |B0000-B3FFF|  mono uses only 4k        | The PCjr and early Tandy 1000
 720k |B4000-B7FFF|                           | BIOS revector direct write to
 736k |B8000-BBFFF|  CGA uses entire 16k      | the B8 area to the Video Gate
 756k |BC000-BFFFF|                           | Array and reserved system RAM
-----------------------------------------------------------------------------
C0000 ***** 64k *************** expansion ROM
-----------------------------------------------------------------------------
 768k |C0000-C3FFF|16k EGA BIOS C000:001E EGA BIOS signature (letters IBM)
 784k |C4000-C5FFF|
      |C6000-C63FF|256 bytes Professional Graphics Display communication area
      |C6400-C7FFF|
 800k |C8000-CBFFF|  16k hard disk controller BIOS, drive 0 default
 816k |CC000-CDFFF|  8k  IBM PC Network NETBIOS
      |CE000-CFFFF|
-----------------------------------------------------------------------------
D0000 ***** 64k ***** expansion ROM
-----------------------------------------------------------------------------
 832k |D0000-D7FFF|  32k IBM Cluster Adapter  | PCjr first ROM cartridge
      |      DA000|  voice communications     | address area.
 848k |D4000-D7FFF|                           | Common expanded memory board
 864k |D8000-DBFFF|                           | paging area.
 880k |DC000-DFFFF|                           |
-----------------------------------------------------------------------------
E0000 ***** 64k ***** expansion ROM
-----------------------------------------------------------------------------
 896k |E0000-E3FFF|                           | PCjr second ROM cartidge
 912k |E4000-E7FFF|                           | address area
 928k |E8000-EBFFF|                           |
 944k |EC000-EFFFF|                           |    spare ROM sockets on AT
-----------------------------------------------------------------------------
F0000 ***** 64k ***** system
-----------------------------------------------------------------------------
 960k |F0000-F3FFF|  reserved by IBM          |    cartridge address
 976k |F4000-     |                           |    area (PCjr cartridge
      |F6000      |  ROM BASIC Begins         |    BASIC)
 992k |F8000-FB000|                           |
 1008k|FC000-FFFFF|  ROM BASIC and original   |
      |           |  BIOS (Compatibility BIOS |
      |           |  in PS/2)                 |
 1024k|      FFFFF|  end of memory (1024k) for 8088 machines
------+----------------------------------------------------------------------
 384k |100000-15FFFF| 80286/AT extended memory area, 1Mb motherboard
 15Mb |100000-FFFFFF| 80286/AT extended memory address space
 15Mb |160000-FDFFFF| Micro Channel RAM expansion (15Mb extended memory)
 128k |FE0000-FFFFFF| system board ROM            (PS/2 Advanced BIOS)
-----------------------------------------------------------------------------

Note that the ROM BIOS has a duplicated address space which causes it to
"appear" both at the end of the 1 megabyte real mode space and at the end of
the 16 megabyte protected mode space. The addresses from 0E0000 to 0FFFFF are
equal to FE0000 to FFFFFF. This is necessary due to differences in the memory
addressing between Real and Protected Modes.