Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!oliveb!sun!burgundy!jborza
From: jborza%burgundy@Sun.COM (Jim_Borza)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Fast video routines...
Message-ID: <81802@sun.uucp>
Date: 15 Dec 88 17:14:54 GMT
References: <45714@yale-celray.yale.UUCP>
Sender: news@sun.uucp
Lines: 25

In article <45714@yale-celray.yale.UUCP>, spolsky-joel@CS.Yale.EDU (Joel Spolsky) writes:
> To my chagrin I have discovered that the "fast-video" routines Turbo-C
> uses are not fast enough for my needs, so I'm writing my own. Here's
> what I think I have to do:
> 
> 	- find out if the display is monochrome using BIOS Int. 11
> 	- if so, display starts at B000:0000
> 	- otherwise, display starts at B800:0000
> 	
> Are there any hardware combinations where this _won't_ work? In other
> words - are there any common display adapters that have their video
> memory elsewhere? and is Int.11 reliable?
> 
> Thanks in advance,
>   Joel Spolsky  

Better to use int 16h (ah=0Fh).  That'll get the *current* video mode (the
user may have >1 Adapter).  If the return is Mode=7, the display is mono-
chrome and the display segment is B000:0.  If it's anything else, you can
force it to Mode=3 with int 16h (ah=0) and use B800:0 (This is assuming
you are using 80X25 TEXT mode - graphics is a tad more complex).  As al-
ways, it is polite to store the mode returned from the inquiry and restore
the original mode on exit.  Monochrome is always Mode=7.  All standard
graphics adapters will accept Mode=3.

Jim Borza