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PC200 DIP switches

The Sinclair PC200 has 6 DIP switches, but only 5 are used.

SW1: Boot drive

If SW1 is off and a second floppy drive is present, then the PC will boot from the second drive. This switchover happens at the BIOS level rather than the hardware, so programs which try to bypass the BIOS and manipulate the drive directly will get confused.

This functionality is present in BIOS 1.5, but not in the earlier 1.2.

SW2,3: Video hardware

SW2 SW3 Hardware
Off Off Built-in chipset emulating MDA, monitor output
Off On Built-in chipset emulating CGA, monitor output
On Off Disable built-in chipset, use add-on card
On On Built-in chipset emulating CGA, television output

SW4,5: Initial Video Mode

SW4 SW5 Video mode
Off Off Add-on EGA or VGA
Off On Add-on or built-in CGA, 40 columns
On Off Add-on or built-in CGA, 80 columns
On On Add-on or built-in MDA, 80 columns

John Elliott 20 June 2009