Date: Sun, 9 Apr 2000 19:05:12 +0600 (LKT) From: Kalum Somaratna aka Grendel X-Sender: root AT darkstar DOT grendel DOT net To: djgpp AT delorie DOT com Subject: Re: HARDWARE INTERRUPT HANDLING BY CWSDPMI In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Reply-To: djgpp AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: djgpp AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk On Sun, 9 Apr 2000, Eli Zaretskii wrote: > > A DJGPP program indeed incurs additional overhead, because under DPMI, > all hardware interrupts are reflected to protected-mode handlers > first, and only if unhandled, they are passed to real-mode handlers. > The mode switch that this involes takes up hundreds of CPU cycles. > In such a case like handling com port interrupts, installing *both* a real mode and a protected mode handler should avoid this overhead. Infact I thought that it was standard practice when writing protected mode programs that handle transmission etc, that a real mode handler should also be installed to avoid any loss as then if a interrupt occurs in real mode, it is handled in real mode itself instead of the normal protected mode switch that taks place. Grendel Hi, I'm a signature virus. plz set me as your signature and help me spread :)