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From: roper@uw-june.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Video Programming
Message-ID: <1929@uw-june.UUCP>
Date: Mon, 2-Feb-87 00:43:56 EST
Article-I.D.: uw-june.1929
Posted: Mon Feb  2 00:43:56 1987
Date-Received: Tue, 3-Feb-87 02:20:55 EST
Organization: U of Washington, CSCI, Seattle
Lines: 39

Can anyone recommend a good reference book providing in-depth
programming information for the various video controller types?  I am
looking for something in the style and price range of say, Norton's book
or Advanced MS-DOS (as opposed to the Options and Adapters Manual).

It should do a thorough job of sorting out the current state-of-affairs
in video adapters, especially the various EGA and PGA standards -- which 
are given the short shrift in both of the aforementioned books. 

Any suggestions would be appreciated.

In the meantime, I have a few questions:

1)  Since only 128K of main memory is reserved for display buffers (from
    A0000 to BFFFF), where do EGA's with "a full 256K of RAM", put the 
    other 128K?  Or is it just bank-switched?

2)  By my calculations, 112K is required for a full page of graphics in
    video mode 10h, using a 16-color palette.  Is the rest of the (128K)
    display memory wasted?

3)  Advanced MS-DOS says that mode 10h uses either a 4- or 16-color palette,
    depending upon the amount of display memory provided by the adapter.
    Is this selection made automatically?  What is the cut-off?

4)  Norton makes a vague reference to the difficulty of writing directly
    to the EGA's display buffer.  What's the story?  Are the pros and cons
    of accessing the EGA's buffer directly any different from say, the MA
    or CGA?



Many thanks.

-- 
---Michael Roper---                    *
                                       *   "Calvin, do you believe in God?"
ARPA:  roper@june.cs.washington.edu    *
UUCP:  ihnp4!uw-beaver!uw-june!roper   *  "Well...SOMEBODY is out to get me."