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