Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!sun-barr!newstop!suntops!hatter.Tops.Sun.COM!rdas From: rdas@hatter.Tops.Sun.COM (Robin Das) Newsgroups: comp.sys.ibm.pc Subject: Re: Can I call a TSR from protected mode? Message-ID: <661@suntops.Tops.Sun.COM> Date: 13 Sep 89 21:58:06 GMT References: Sender: news@suntops.Tops.Sun.COM Reply-To: rdas@hatter.tops.sun.com (Robin Das) Distribution: comp Organization: Sun Microsystems, Inc. Mt. View, Ca. Lines: 16 In article kevin@harpo.doc.ic.ac.uk (Kevin Twidle) writes: >I have a TSR that I want to be able to call from a protected mode >program running under DOS. This really boils down to causing an >interrupt in protected mode. > >I know nothing about protected mode :-( It this possible? easy? hard? >Can anyone give me some names of any good books on the subject? > Protected mode has a different interrupt system. Any interrupts that occur look into the IDT (interrupt descriptor table) to determine the vector. You need to switch modes back down to Real Mode and then re-issue the interrupt. Any results need to be copied back to protected mode. With a DOS extender like Rational Systems' DOS 16/M, it can be done with some effort. Without an extender, you are going to have a really tough time with this problem.