Re: vertical retrace inte

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#585

From: Dave Stampe-Psy+Eng
Date: Tue, 11 Aug 1992 21:45

19 lines
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>It's not that simple.  The problem lies in the actual interrupt signal.
>Almost all cards drive the line high or low, rather than using a pull up
>resistor and driving the line low.  So if two cards try to share an interrupt,
>they would end up fighting, with one card driving high, and the other driving
>low.
>
>A definite 11 year old design fault.

You bet!  They don't even have a pullup resistor on the motherboard,
so you can't just add diodes or open-collector gates to share the lines
(I've tried).


--------------------------------------------------------------------------
| My life is Hardware,                    |                              | 
| my destiny is Software,                 |         Dave Stampe          |
| my CPU is Wetware...                    |                              | 
| Anybody got a SDB I can borrow?         | dstamp@watserv1.uwaterloo.ca |
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Message-ID: <Bsu9ry.G0H@watserv1.uwaterloo.ca>

Path: arc1-ca.pugleaf.net!sparky!uunet!utcsri!torn!watserv2.uwaterloo.ca!watserv1!dstamp

References: <713530461.8643@zooid.guild.org>

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Newsgroups: rec.games.programmer
Path: arc1-ca.pugleaf.net!sparky!uunet!utcsri!torn!watserv2.uwaterloo.ca!watserv1!dstamp
From: dstamp@watserv1.uwaterloo.ca (Dave Stampe-Psy+Eng)
Subject: Re: vertical retrace inte
Message-ID: <Bsu9ry.G0H@watserv1.uwaterloo.ca>
Organization: University of Waterloo
References: <713530461.8643@zooid.guild.org>
Date: Tue, 11 Aug 1992 21:45:33 GMT
Lines: 20

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