FreeGEM video drivers
=====================

  This zipfile contains five 'preferred' FreeGEM video drivers. These should
work correctly on the great majority of PC-compatible hardware. If you cannot
get a usable display out of any of these drivers, you may like to try the
'alternative' drivers zipfile, which should be available wherever you got 
this one.
  
  Use SDVES9.VGA if you have a VESA-compatible video card capable of 800x600
graphics.

  Use SDUNI9.VGA if you have a VGA, an MCGA, or an EGA with an EGA monitor
and sufficient onboard memory (128k or more should be enough).

  Use SDCAT9.EGA if you have a CGA (it also supports the "AT&T" 640x400 
mode on the AT&T 6300, Toshiba 3100e, DEC VAXmate etc.). 

  Use SDHRC9.EGA if you have a Hercules card. 

  Use SD2569.VGA if you have a VESA-compatible video card capable of 
1024x768 graphics in 256 colours (but note that some GEM programs do not 
get on well with a 256-colour screen; see below).

  If you have an EGA with only 64k (or one that's using a non-EGA monitor), 
then although you can use SDCAT9.EGA you'd almost certainly get better results
with one of the EGA drivers from the alternative set.

  Compared to the original GEM drivers, these drivers have the following 
changes:

* Loadable codepages, using code from ViewMAX II. To get this working, you 
  need to install GEM.CPI in the same place as GEMVDI.EXE, and then use CHCP 
  to select the correct codepage before starting GEM.

* There is one extra function, which I've called v_delay(). It's simply a 
  wrapper around the BIOS's microsecond delay functionality, and provides 
  correct window opening/closing effects on the latest FreeGEM AES.

* The mouse support in all drivers has been updated to match ViewMAX/1. There
 is one visible change to this: if you have the mouse type set to 0 (no mouse)
 then pressing CTRL and the right SHIFT key together toggles whether the 
 pointer is visible. It also tries to pick up COM port settings from the BIOS 
 rather than hardcoding them.

* Some of the other bits of code have also been updated to match ViewMAX/2. 
 In general the changes are minor, and relate to support for the 'universal'
 EGA/VGA and CGA/AT&T drivers.

256-colour driver compatibility issues
======================================

* Most programs (including, I'm afraid, anything I've written that uses 
  colour) won't accept that there are more than 16 colours available. For 
  example, if you want to use colours 17-255 as colours for screen elements, 
  you'll have to edit GEM.CFG manually. Developers should also be aware 
  that AES object definitions only allow 16 colours, since they use 4-bit 
  colour numbers. If you want any more, you'll have to use G_USERDEF objects 
  or ViewMAX-style colour categories.

* The 1024x768 driver makes GEM very memory-hungry (because all the bitmaps it
  needs to store are suddenly twice as big, or bigger, than in VGA mode). The
  drawing programs (Doodle and Paint) try to allocate 768k, fail, and refuse to
  run.

Other compatibility issues
==========================

  VIDPATCH.EXE has been supplied in case the automatic video mode probes 
in SDUNI9.VGA or SDCAT9.EGA do not work as expected. The following commands
override the probe:

VIDPATCH SDUNI9.VGA 0	  -- force EGA mono
VIDPATCH SDUNI9.VGA 1	  -- force EGA colour
VIDPATCH SDUNI9.VGA 2	  -- force VGA/MCGA mono
VIDPATCH SDUNI9.VGA 3 	  -- force VGA colour
VIDPATCH SDUNI9.VGA AUTO  -- go back to automatic probe

VIDPATCH SDCAT9.EGA 6	  -- force CGA mode
VIDPATCH SDCAT9.EGA 64	  -- force AT&T 6300 mode
VIDPATCH SDCAT9.EGA 116	  -- force Toshiba 3100e mode
VIDPATCH SDCAT9.VGA AUTO  -- go back to automatic probe


