There is a certain amount of complexity in the translation of PC video modes to RISC OS video modes. Most of the time you need not concern yourself with this, but for some software you may need to refer to this section to determine the capabilities of the PC Card/host combination.

Mode 27 is used for VGA: 640 X 480 X 16 graphics display in DOS. 

Mode 31 is used for SVGA 800 X 600 X 16 graphics display in DOS. (DOS mode 6Ah). The standard DOS text screen (80 X 25) is actually 640 X 400 pixels. There is no such mode under RISC OS so 640 X 480 is used instead. This results in 40 unused pixels at the top and bottom of the display, making it a bit more `letterboxy' than a typical PC display. 

• Note that the default definitions of modes 27 and 31 for the AKF60 monitor give a slow refresh rate (60Hz) and thus a flickery display. We recommend that you edit the monitor definition file to comment out the slow 640 X 480 and 800 X 600 modes. Contact Aleph One if your are unsure about this.

If a mode !PC doesn’t know how to handle is selected, it will always check with RISC OS to see if such a mode can be displayed. If the mode cannot be displayed then !PC reverts to multitasking, and displays the mode in a window of the correct size. 
 

1. Use the Save sprite feature (see Switching between PC Card modes on page 32) to save a copy of the screen.
2. Load this into !Paint to find the size and colour depth of the screen.
3. Create a suitably shaped mode to enable you to use the software in single-tasking mode.

To stop this happening, change your monitortype to reflect the actual type of your monitor. 
 

• 16-colour graphics, using 4 video planes as VGA, up to 524288 pixels

 
• 256-colour graphics, based on mode 13h, up to 65536 pixels

 
• 256-colour graphics using Plane Mask / Read Plane Select registers (as 360 X 480 X 256 mode), up to 262144 pixels