From owner-freebsd-hardware  Sat Oct 31 20:47:42 1998
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To: John Polstra <jdp@polstra.com>
cc: Greg Lehey <grog@lemis.com>, hardware@FreeBSD.ORG
Subject: Re: Mixing 8- and 16-bit shared memory ISA cards 
In-reply-to: Your message of "Sat, 31 Oct 1998 20:31:07 PST."
             <199811010431.UAA24975@austin.polstra.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Sat, 31 Oct 1998 20:48:46 -0800
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>> It affects all machines with ISA busses, not just early x86. The ed
>> driver goes to great pains, however, to attempt to work around this
>> problem by putting 16bit cards into 16bit memory mode only while
>> actually accessing them.  The rest of the time they are left in 8bit
>> mode. So you should be able to mix them in the same 128K region in
>> this specific case, but GENERALLY you cannot.
>
>Thanks for the info!  That explains why I didn't see problems when I
>"should" have.
>
>Speaking of such matters ... The manual for my SMC 8013 card says that
>the card can be put into either an 8-bit or a 16-bit slot.  (It's a
>16-bit card.)  But when I tried putting it into an 8-bit slot, and set
>flags=0x2 to force 8-bit mode, the probe said something like "failed
>to clear shared memory."

   Yeah, don't do that. :-)

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project

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