From: "John Welter" <jwelter AT nwgeo DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Newbie Question.....
Date: Mon, 23 Feb 1998 08:44:42 -0700
Lines: 35
Organization: North West Group
NNTP-Posting-Host: 207.153.6.200
Message-ID: <34f1997c.0@news.oanet.com>
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

I've been looking at porting a 16 bit DOS soft realtime application to a 32
bit environment for some time now and hence I stumbled across this list.  In
other words, I've got a few questions about DJGPP:

1) I understand programs written with it run in protected mode.  Under what
circumstances do they switch back to real mode?  Ie: when doing screen or
file I/O?  Or are the included libraries all protected mode?  I assume file
I/O is still via DOS/BIOS so a switch to real mode is required?  Basically,
I'm trying to come to some understanding as to how much time is still spent
in real mode as it affects some ISR's we need to write that must execute
with low latency.

2) Does anyone have code for a 32 bit filesystem for DJGPP?  Some products
such as Phar Laps ETS system have this as an optional add on to avoid having
to use DOS/BIOS for file I/O and thus avoiding a switch to real mode.

3) Same as #2 but with respect to screen (text) I/O?

4) Are bi-mode ISR's supported?

Basically, I'd much rather use DJGPP then PharLap's stuff as the price is
certainly better and having full access to source is always a good thing but
I'm not sure if there are any gotcha's with DJGPP.

We also looked at QNX but require the ability to boot to DOS and then start
executing the application which QNX doesn't allow.

Please reply via email if possible, thanks.

John Welter
MCSE, Systems Engineer
North West Group