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From: craig@mstr.hgc.edu (craig chaiken)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Calling INT 25H and 26H from INT 28H
Message-ID: <581@mstr.hgc.edu>
Date: 4 Oct 90 05:17:43 GMT
Sender: news@mstr.hgc.edu
Reply-To: craig@mstr.hgc.edu (craig chaiken)
Organization: The Hartford Graduate Center, Hartford CT.
Lines: 22


I have unsuccessfully attempted to execute INT 25H and 26H (read and write
absolute disk sectors) from an INT 28H (DOS Idle) handler.  Here is what
happens:

1)	The TSR loads successfully, and returns to the DOS prompt.
2)	Additional commands may be entered without difficulty at this point.
3)	A remote computer triggers the execution of an unlimited number
	of INT 25H or 26H functions without difficulty.
4)	The host computer is allowed to sit dormant for a moment.
5)	A user attempts to enter a command at the DOS prompt on the host.
6)	The host computer's keyboard locks up, except for acknowledging
	<CapsLock>, <NumLock>, and <ScrollLock>.
7)	The TSR stops processing requests.

My guess is that INT 25H and 26H somehow corrupt DOS's keyboard handler
stack (IOStack).  The only solution I can think of is to rewrite INT 25H
and 26H making certain to use a separate stack.  If some MSDOS guru out
there knows a better solution, I would greatly appreciate a hint.

Craig Chaiken
craig@mstr.hgc.edu