Xenix/386 and VGA

[brian chapman]

In article <712 at applix.UUCP> jim at applix.UUCP (Jim Morton) writes:
< SCO Xenix/386 release 2.2.3 supports booting and running on Compaq-VGA
< compatible boards (Paradise chip set) as if it were an EGA. 
< 
< I'm told release 2.3.X, due out in July, will also provide graphics
< level access to the VGA, so application programs can use the 640x480
< modes by opening /dev/vga.

/dev/vga or /dev/ega is too low a hardware level device
for most uses.

/dev/ega means *the* ega adapter.

1 If what you really have is an VGA, then /dev/ega
  won't open.  Even if all you want to draw is a
  simple 320x200 B&W graph that can be done on a cga,
  ega or vga.

2 The adapter device is not associated with any multiscreen.
  /dev/ega is the EGA video device and write()s to it appear
  on the currently displayed screen.

Most needs can be met using a multiscreen file descriptor.

1 The CGA, EGA and VGA are increasing super sets of graphic
  functionality so all the EGA modes works on VGAs and all the
  CGA modes work on EGAs and VGAs.  So simple CGA type
  graphs can be drawn on the current multiscreen without
  a lot of hardware type sorting out.  (unless you have a MONO)

2 There are ioctls to query what kind of adapter is in use.
  So a programs can determine what is the maximum level of
  graphics functionality available and tune their output to
  the level supported by the hardware, using 4 color
  graphs on the CGA and 256 color on the VGA.
-- 
Brian Chapman	 uunet!sco!chapman