Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!usc!apple!vsi1!zorch!ditka!nfsun!eklektik!thomas
From: thomas@eklektik.UUCP (/dev/tty000)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Bridgeboard questions
Summary: Video Co-Existing
Message-ID: <1471@eklektik.UUCP>
Date: 4 Apr 90 23:08:08 GMT
References: <3RXG4AM@drivax.UUCP>
Reply-To: thomas@eklektik.UUCP (/dev/tty000)
Followup-To: 3RXG4AM@drivax.UUCP
Organization: Computers, Gerbils, and Games in the Basement, Pgh, PA
Lines: 33

In article <3RXG4AM@drivax.UUCP> liberato@drivax.UUCP (Jimmy Liberato) writes:
>This one is almost verging on comp.sys.ibm.pc.  Sorry!
>
>I have been experimenting with a Genoa Super VGA card -- not mine, :-( 
>in the A2088.  Though I have had complete success I am puzzled about
>something.  How is it that I am able to have both CGA and VGA exist
>simultaneously?  That is, both the Amiga CGA emulation and the VGA
>are active at the same time.  I had thought this was impossible; that
>the video bios areas would overlap.  Now, I've often seen Mono and VGA
>coexist on the same machine (a common debugging setup on '386 machines)
>and that is how I thought I would have to do this but it works fine from
>the PC Color window with another monitor for the VGA.  Am I simply 
>incorrect in what I thought was true or are some naughty things happening
>in the video bios addresses that will bite me when I'm not expecting it?

   Ok, for everything I know about the PC you should be fine.  If I remember
my PC memory map right, the area for the VGA adapter in memory is in a
different area than for a CGA adapter.  In the memory for the PC there is a
certain area, (about $A000 I believe) for video boards to occupy and I think
the CGA board goes into a lower address than the VGA board.  I will have to
look this up in Peter Norton's book tomorrow and let you know for sure.  If
someone else knows otherwise on this please set me and Jim straight.
 
>Jimmy Liberato   ...!amdahl!drivax!liberato 

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