[comp.sys.ibm.pc] VGA,EGA,CGA question

calexand@castor.usc.edu (Craig Alexander) (01/12/89)

I have a simple question for any of you out there who is willing to
answer.  I have just purchased an IBM PS2 Model 30/286 machine
with VGA graphics.  My question is, If I purchase sotware which
supports EGA graphics, will my VGA system output EGA or CGA graphics???

Thanks in advance...



      >==========================>
   >==== Craig Alexander ====>
>=======================>

chasm@killer.DALLAS.TX.US (Charles Marslett) (01/13/89)

Virtually all EGA software will run perfectly on a VGA (the exceptions
are limited to a few programs that are very much optimized for a special
environment -- high speed graphics terminal emulation programs, for
example).  To a lesser extent, the same applies to running CGA software.
The VGA has a bit in CRTC register 0x11 that is used to disable writes
to several of the registers that CGA software often writes to... the
effect is that often such non-EGA compatible software can be made to work
much better on a VGA than on an EGA (as opposed to the autoswitching EGAs
like ATI's that run in a real CGA mode when such software is invoked).

Charles
chasm@killer.dallas.tx.us