Amstrad XT pages PC1640 DIP switches
The PC1640 has 10 DIP switches, which control its internal graphics adaptor.
(See also the technical manual, section 1.22.)
SW1-5: IGA hardware emulation and initial graphics mode
Valid combinations are:
| SW1 | SW2 | SW3 | SW4 | SW5 | Hardware mode |
|---|---|---|---|---|---|
| Off | Off | On | Off | Off | EGA with mono monitor (DISPLAY MDMONO) |
| On | On | On | Off | Off | EGA with EGA monitor, 200 lines (DISPLAY ECD200) |
| Off | On | On | Off | Off | EGA with EGA monitor, 350 lines (DISPLAY ECD350) |
| Off | Off | Off | On | On | EGA with CGA monitor, 80 column (DISPLAY CDCOLOR) |
| On | Off | Off | On | Off | EGA with CGA monitor, 40 column |
| Off | On | Off | On | Off | Secondary EGA, mono monitor |
| Off | Off | On | On | Off | Secondary EGA, EGA monitor, 350 lines |
| On | Off | On | On | Off | Secondary EGA, EGA monitor, 200 lines |
| Off | On | On | On | Off | Secondary EGA, CGA monitor |
| Off | Off | On | Off | On | MDA (DISPLAY MDTEXT) |
| Off | Off | Off | On | On | CGA 80 column (DISPLAY CDMONO) |
| On | Off | Off | On | On | CGA 40 column |
| Any | On | Off | On | On | Secondary MDA |
| Any | On | On | On | On | Secondary CGA |
Notes:
- If SW5 is on, the hardware emulates a genuine 6845.
- The 'secondary' combinations are for when an additional CGA or MDA card is present and should be used as the primary display.
SW6, SW7: Select IGA font
If SW9 is turned on, then SW6-7 select the font used by the IGA. If it is turned off, then the English font is used.
| SW6 | SW7 | Font variation |
|---|---|---|
| Off | Off | Danish |
| On | Off | Portugese |
| On | Off | Greek |
| On | On | English |
SW8: Monitor type
This switch should be turned on for an EGA monitor, off for an MDA or CGA monitor.
SW9: Enable 32k of EGA ROM
A genuine EGA has a 16k ROM. Turn this switch off to make the PC1640's internal graphics adaptor limit itself to a 16k ROM for strict EGA compatibility, or on to use the full 32k ROM. If SW9 is turned off, then the font selection switches SW6 and SW7 are ignored.
SW10: Disable internal graphics adaptor
If this switch is turned on, the internal graphics adaptor is disabled. With the IGA disabled, switches 1-5 and 8-9 are ignored, and switches 6-7 specify the type of the add-on video adaptor:
| SW6 | SW7 | Video mode |
|---|---|---|
| Off | Off | Add-on EGA or VGA |
| On | Off | Add-on CGA, 40 columns |
| Off | On | Add-on CGA, 80 columns |
| On | On | Add-on MDA |
John Elliott 12 April 2003