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From: "David Alderman" <dave@persprog.com>
Organization: Personalized Programming, Inc.
To: Narvi <narvi@haldjas.folklore.ee>
Date: Thu, 25 Apr 1996 13:55:34 EST
Subject: Re: Boot floppy problem with Intel Atlantis motherboard (Ma
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Narvi wrote:
> 
> 
> 
> On Thu, 25 Apr 1996, Michael Smith wrote:
> 
> > Brett Glass stands accused of saying:
> > > 
> > > > Use -c and turn off all the sio ports (especially sio3).  
> > > 
> > > Is this the S3 video chip vs. COM4: conflict?
> > 
> > Actually, S3 parts are very tolerant of activity on that port.
> > Sadly, the ATI Mach64 chips _aren't_, and these are the ones that cause
> > problems.
> 
> Some do have the conflict - you can't use some older (and I don't know 
> about newer) serial cards/modems with Trio64V+ - The system still works 
> (at least with DOS + Windows) but you can't access the serial.
> 
> > 
> > It all started with IBM and the 8514...

I believe the problem in both cases derives from the fact that most 
serial ports do not use 16 bit I/O addresses - they usually ignore 
the most significant 4 bits.  Therfore a serial port at x3E8H will 
confilct with a video device at (let's say) 33E8H.  I believe some of 
the S3 chips fall into this category.  I can't remember if the 
original IBM serial ports had 12 or 16 bit addresses (I have the old 
schematics around here somewhere) so the 8514 might have been OK with 
IBM serial hardware.  I believe I bought a 4 port serial board once 
that was 16-bit addressable specifically to get around this problem 
with an S3 board.  I'll bet the company's out of business for 
spending the extra four cents required to put a 16 bit PAL on the 
board instead of just a 12 bit one.  
======================================
When philosophy conflicts with reality, choose reality.
Dave Alderman  -- dave@persprog.com
======================================