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From: bcw@rti.UUCP (Bruce Wright)
Newsgroups: comp.sys.ibm.pc
Subject: Re: CGA emulation on EGA???
Summary: EGA does not quite emulate CGA
Message-ID: <3289@rti.UUCP>
Date: 28 Nov 89 14:28:13 GMT
References: <QZQP8Qe00WB6AlN2I6@andrew.cmu.edu>
Organization: Research Triangle Institute, RTP, NC
Lines: 24

In article <QZQP8Qe00WB6AlN2I6@andrew.cmu.edu>, rh1m+@andrew.cmu.edu (Rudi Jay Halbright) writes:
> CGA software should run w/o modification on an EGA.  Ask your friend to 
> try it.

This is not quite true.  Most (90+%) CGA software will run properly on an 
EGA without modification, but the EGA does not provide 100% emulation of a
CGA.  For example, there are several registers in the controller which
either mean different things or which are simply ignored on the EGA.  The
most common problem is that the colors come out wrong (but still readable)
on the EGA, which is unfortunate but not a disaster.  There are other
possible incompatibilities which can cause things to fail to work at all,
but very little software ever used them.

There are some programs floating around which attempt to set up the EGA
to reduce the probability of problems.  I don't have any experience with
them (I haven't encountered anything that I couldn't persuade to run after
a reasonable fashion), so I can't make any comments on which ones work
best or how often they fix the problems, but I know they exist.

Your friend should still try running the CGA software on the EGA if it
hasn't already been tried - the probability is overwhelming that it will
work acceptably on the EGA.

						Bruce C. Wright