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From: brent@rtech.UUCP (Brent Williams)
Newsgroups: comp.sys.ibm.pc
Subject: Anyone have code fragment for CGA snow elimination?
Message-ID: <957@rtech.UUCP>
Date: Wed, 24-Jun-87 00:22:34 EDT
Article-I.D.: rtech.957
Posted: Wed Jun 24 00:22:34 1987
Date-Received: Fri, 26-Jun-87 04:12:46 EDT
Distribution: na
Organization: Relational Technology, Alameda CA
Lines: 43


I have been looking for a way to eliminate "snow" from a CGA adapter
during text display.  I'm writing directly to the frame buffer as most 
people do (the BIOS is too slow for what I'm up to).  I've been looking
through the IBM PC BIOS source listing and have found the loop where they  
go and wait for vertical retrace before proceeding to write the character
to the screen.  I have been trying with little success to understand 
the other stuff they do.  They turn the video back off then back on and 
reset a register or two once the I/O has completed.  

My questions, in order of utility:

1.	Does anyone have a public-domain code fragment that clearly shows
	how to write alpha text to the CGA without snow, so that I don't 
	have to try to wade further through mounds of assembler code that
	I would rather not read?

2.	If such is not available, could someone please give information on
	commercial source library packages that do direct frame buffer access
	but also contain assembler source code?

3.	Can anyone recommend a book that has all the necessary information on
	how to do this that is comprehensible to a C programmer with some 
	understanding of Assembler?  I already have both of Peter Norton's 
	books, but they don't have enough information.

4.	Is it really necessary to go through all the saving and restoring of 
	video status that IBM does in the BIOS?  Any other comments along this
	line would be helpful.

I will summarize and post any replies received by mail if anyone asks.


Thanks, 


-- 
-brent williams
 Relational Technology, Inc.
 1080 Marina Village Parkway
 Alameda, CA   94501

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