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From: ben@catnip.UUCP (Bennett Broder)
Newsgroups: net.micro.pc
Subject: Re: CGA vs EGA
Message-ID: <355@catnip.UUCP>
Date: Sat, 11-Oct-86 19:55:43 EDT
Article-I.D.: catnip.355
Posted: Sat Oct 11 19:55:43 1986
Date-Received: Sun, 12-Oct-86 13:23:19 EDT
References: <2105@ecsvax.UUCP>
Reply-To: ben@catnip.UUCP (Bennett Broder)
Distribution: net
Organization: The Broder Residence, Holmdel, N.J.  07733
Lines: 49

In article <2105@ecsvax.UUCP> uchuck@ecsvax.UUCP (Charles Bennett) writes:
>
>We are currently getting ready to purchase new IBM PC/AT's for the
>programming staff here.  We utilize the machines in a variety of ways
>both for microcomputing and accessing mainframes via async communications
>and will be adding an IRMA-X type board for 3279 emulation.  We have a
>large investment in software, most of which uses color but not
>necessarily pure graphics.  The question is this; what, if any, are
>the incompatablities between the CGA board and the EGA board (with
>appropriate monitor, of course).  Rumor postulates two completely
>different circumstances; 1) CGA software does not run on the EGA, and
>2) CGA software runs on the EGA but in CGA mode without special
>intervention.  ????WHAT IS THE STORY????  !!!!PLEASE!!!!


The answer is not so simple.  It depends on both the EGA board and the
software.  The least compatible board you can buy is the IBM.  It contains
the documented CGA video modes, but not the CGA registers.  This means that
software that accesses the video board properly (through BIOS calls) will
work, but software that attempts to program CGA registers directly will not
work.  I think you will find about a 70% success rate, slightly worse for
games.  Some of the clone boards do quite a bit better.  The Quadram QEGA+
and similar boards are supplied with ram-resident software that when
installed make it possible for most programs that program the CGA
directly to work.  I have found this works with about 90% of all CGA
software.  The remaining "trouble" programs are those that are copy
protected and must boot from floppy (since the ram-resident software is
lost on re-boot), and those that use undocumented CGA modes (like the 16
color mid-res graphics).  The most compatible board I have seen is the
"vu-tek",  which has special soft switches to place the board in CGA
emulation, and which supports the undocumented modes.  (The emulation is
so accurate it even flickers when the screen scrolls!)  Since the cga
emulation is not lost when you re-boot, even copy protected software runs.
The vu-tek runs every piece of CGA software I have ever tried. (I wish I
knew about the vu-tek when I bought my QEGA+)  

In conclusion, I would highly recommend that you opt for EGA boards in
your new machines.  I consider the text that the CGA produces unacceptable
for more than just casual use; I don't think I could program all day on
a CGA monitor.  If you are concerned about CGA compatibility, be sure
to have your dealer test the CGA software you intend to run to see if
it will work on the EGA card he is trying to sell you.


-- 

Ben Broder
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