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From: TRL3@psuvm.psu.edu (Tim Larson)
Newsgroups: comp.sys.ibm.pc,alt.msdos.programmer
Subject: Re: EGA 43 line mode.  Cursor is missing
Message-ID: <90048.165401TRL3@psuvm.psu.edu>
Date: 17 Feb 90 21:54:01 GMT
References: <85@leedat.UUCP>
Organization: Penn State University
Lines: 23

Sorry to post rather than mail, but my mail to the original poster bounced.
This subject may be of general interest anyway.

The original post asked why the cursor disappeared after switching the
EGA to 43 line mode.

On the EGA, cursor emulation is implemented by adding 5 to any Cursor
Start or Cursor End value greater than 4 (since the original character
matrix was 8 lines high, but the EGA is 14, this provided compatability
with old CGA software).  However, you are changing the character matrix
back to 8 lines high, so simply disabling cursor emulation should work.
Change bit 0 of the Video Display Data Area INFO byte (0040:0087) to 1
(leaving other bits unchanged) *before* calling INT 10H function 01H.

By the way, the VGA takes the character height into account, so this
information is EGA-specific.

(Source: "Programmer's Guide to PC & PS/2 Video Systems," Richard Wilton,
[Redmond, WA: Microsoft Press], 1987.  An excellent book, BTW :))

Cheers!
-Tim Larson
trl3@psuvm.bitnet