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Date:      Wed, 2 Dec 1998 18:14:09 -0700
From:      Nate Williams <nate@mt.sri.com>
To:        Mike Smith <mike@smith.net.au>
Cc:        David Dawes <dawes@rf900.physics.usyd.edu.au>, Peter Jeremy <peter.jeremy@auss2.alcatel.com.au>, current@FreeBSD.ORG
Subject:   Re: sio breakage 
Message-ID:  <199812030114.SAA10483@mt.sri.com>
In-Reply-To: <199812030107.RAA01213@dingo.cdrom.com>
References:  <19981203115222.A3051@rf900.physics.usyd.edu.au> <199812030107.RAA01213@dingo.cdrom.com>

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> > >I agree.  And whilst I haven't checked why, XFree86 does appear to
> > >disable interrupts at times.
> > 
> > I agree too, but it does disable interrupts when probing for fixed pixel
> > clocks (which is mostly only done for obsolete hardware), and sometimes
> > when programming PLLs.  If someone has a better way of handling time
> > critical thing like this (preferably in a portable way), please let me
> > know.  I'd love to dump our disable interrupt code.
> 
> I get the impression from this though that you only do interrupt 
> disables when probing or changing video modes, is that correct?

I get that impression as well.

> The entire train of angst here is descended from percieved problems in 
> interrupt delivery during normal operation; if you're only disabling 
> interrupts during startup then this prettymuch exonerates the X server.

Except that I can say with assurance that at least older versions of the
XFree86 server *seem* to be disabling interrupts for long periods, or at
least calling code that disables interrupts.  When I switched to the XIG
(XInside at the time) server, all of my serial overflows went away.

That was the *only* configuration difference.  To be sure, I even
re-configured the XFree86 server and the problem re-occurred.  Swapped
it back and it went away.

Note, this was about a year ago, maybe more so it may have changed.
(The box in question has a S3 928 card in it..)



Nate

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