The XT (8 Expansion slots and upgraded power supply) had a single bank of eight DIP switches:

1: Always OFF
2: OFF - math-co-processor (8087) installed, ON - math co-processor not installed
3: OFF, 4: ON - only 128K RAM installed
3: OFF, 4: OFF- 256K or more RAM installed
5: ON, 6: OFF - color monitor
5: OFF, 6: OFF - monochrome monitor
7: ON, 8 ON - single floppy drive
7: OFF, 8: ON - dual floppy drive.

The PC (5 expansion slots and 65W power supply) had two banks of eight DIP switches:

BANK ONE

SWITCHES 1, 7, and 8 indicate the number of floppy drives:
1,7, and 8 ON - ZERO drives
1, OFF, 7 and 8 ON - ONE drive
1 and 7 ON, 8 OFF - TWO drives
1 and 8 OFF, 7 ON - THREE drives
1, 7, and 8 OFF - FOUR drives

Switch 2: NOT USED - MUST BE ON

Switches 3 and 4 indicate the amount of memory on the system board:
For 16K - 3 and 4 ON
For 32K - 3 OFF, 4 ON
For 48K - 3 ON, 4 OFF
For 64K to 256K (or greater) - 3 and 4 OFF

Switches 5 and 6 indicate the display:

5 and 6 ON - NO display
5 OFF, 6 ON - COLOR (CGA 40 X 25)
5 ON, 6 OFF - COLOR (CGA 80 X 25)
5 and 6 OFF - Monochrome (or more than one display adapter)

BANK TWO

switches 1, 2, 3, 4, and 5 indicate memory options
switches 1, 2, 3, 4, and 5 ON - 16K to 64K
switches 1, 3, 4, and 5 ON, 2 OFF - 128K
switches 1, 2, 4, and 5 ON, 3 OFF - 192K
switches 1, 4, and 5 ON, 2 and 3 OFF - 256K (or greater)

switches 6, 7, and 8 NOT USED - MUST BE OFF

NOTE: For both the PC and the XT (including clones), the DIP switches on the motherboard have NOTHING to do with installing a hard drive! The hard drive is controlled by the BIOS on the hard drive adapter card. There will very likely be switches and/or jumpers on the adapter card that will need to be set for different hard drives.



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