Path: utzoo!attcan!uunet!sco!chapman
From: chapman@sco.COM (Brian Chapman)
Newsgroups: comp.unix.xenix
Subject: Re: user doing direct I/O
Message-ID: <7329@scolex.sco.COM>
Date: 1 Aug 90 07:07:51 GMT
References: <3612@sactoh0.UUCP> <1990Jul29.232335.23039@metro.ucc.su.OZ.AU>
Sender: news@sco.COM
Lines: 17


glenn@extro.ucc.su.OZ.AU (Glenn Geers) writes:

>	<...>  However, you still don't get around the system
>call overhead. This can only be achieved by issuing ioctl(fd, IOPRIVL, 1)
>(1 system call, finished) and then banging away at i/o ports in assembler. For
>*fast* graphics <...>

Yes,  direct use of IN & OUT 386 instructions is possible from user
space after giving the [EV]GA_IOPRIVL command.  BUT...  this is
only for use with the video I/O ports.  You will find that Xenix
lets to access all I/O ports but SCO _Unix_ behaves in the more
restrictive manner.
	-- Chapman
-- 
Brian Chapman		uunet!sco!chapman
Pay no attention to the man behind the curtain!