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Date: Sun, 11 Feb 1996 21:15:51 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199602111015.VAA04847@godzilla.zeta.org.au>
To: bugs@freebsd.org, dbacher@dayton.net
Subject: Re: Can't locate 16450 UART when turbo engaged
Sender: owner-bugs@freebsd.org
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>This is a minor problem that I am going to fix on my own, but a 16450 
>UART appears to be detected ONLY when the processor (486DX4/100 AMD) is 
>running in slow mode.  BIOS I/O settings do NOT help, Cache settings do 
>NOT help.

Is it a real 16450?

>I believe that this is caused by an incorrect delay loop (most 
>likely processor dependent) in your detection code.  This is the only 
>explanation as to why the UART works fine (and is correctly autodetected) 
>under PC-DOS 7 and OS/2 Warp, but is misidentified by FreeBSD.

The sio driver has timing problems with internal modems, but these are
because there are no delay loops at all in certain places.

Bruce