XT Switch Settings

 This topic discusses the switches as defined for IBM logoed PCs only.  On
 PC-compatible computers, there may be more or fewer switches and they may
 have different meanings.

 The IBM XT has a single bank of DIP switches.  They are summarized as
 follows:

      SW1 (XT)
ON ╓1┬2┬3┬4┬5┬6┬7┬8╖
 ↑ ║▄│ │   │   │   ║
   ╙╥┴╥┴─┴─┴─┴─┴─┴─╜
    ║ ║ ╚╦╝ ╚╦╝ ╚═╩═► 7-8: diskette drives
    ║ ║  ║   ╚══════► 5-6: initial active display monitor
    ║ ║  ╚══════════► 3-4: system board RAM
    ║ ╚═════════════► 2: 8087
    ╚═══════════════► 1: POST loop (always OFF)

 Positions 2,5-6,and 7-8 are the same as on the PC. See PC Switch Settings

█▌XT RAM▐█
 The XT POST determines the total system memory by scanning RAM address
 space to locate 32K blocks (it displays numbers in the top left corner of
 the screen as it does this).  Therefore, you do not need to change switch
 settings when you add or remove memory option cards.  Moreover, you need
 not populate the system board fully (above 128K) to add additional memory
 option cards.

 Switches 3-4 indicate the memory on the XT system board as follows:

       SW1 (XT)
ON ╓1┬2┬3┬4┬5┬6┬7┬8╖
 ↑ ║ │ │▄│▀│ │ │ │ ║  128K
   ╙─┴─┴─┴─┴─┴─┴─┴─╜
ON ╓1┬2┬3┬4┬5┬6┬7┬8╖
 ↑ ║ │ │▀│▄│ │ │ │ ║  192K
   ╙─┴─┴─┴─┴─┴─┴─┴─╜
ON ╓1┬2┬3┬4┬5┬6┬7┬8╖
 ↑ ║ │ │▄│▄│ │ │ │ ║  256K
   ╙─┴─┴─┴─┴─┴─┴─┴─╜

See Also: Equipment List
          Switch Settings
                                    -♦-