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From: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
Message-Id: <199606080739.AAA13057@GndRsh.aac.dev.com>
Subject: Re: Which dual Pentium motherboard? Cyrix SMP?
To: Brett_Glass@ccgate.infoworld.com (Brett Glass)
Date: Sat, 8 Jun 1996 00:39:00 -0700 (PDT)
Cc: sef@kithrup.com, questions@FreeBSD.org, freebsd-hardware@FreeBSD.org
In-Reply-To: <9605078341.AA834195613@ccgate.infoworld.com> from Brett Glass at "Jun 7, 96 07:57:30 pm"
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> > However, EISA requires motherboard and NVRAM configuration for *all* of
> > the cards, be they ISA or EISA.
> 
> Nope. ISA cards work without configuration in an EISA system, so long as
> there are no conflicts. This is because configuration files are not
> available for most ISA cards. (Some manufacturers created "generic ISA
> device" configuration files, but system integrators tended not to use them.
> The systems still worked.)

Correct, for _pure_ ISA cards.

> 
> > If, as Rod suggested, the floppy controller is on an already-configured
> > EISA card, and you move it to a different slot or different motherboard,
> > you are quite likely to be hosed.
> 
> Actually, this is generally NOT true. Even though it's an EISA card, the
> floppy controller is usually just an ISA interface that's "coming
> along for the ride" on the same physical board. It is usually enabled by a
> jumper. Sometimes, the EISA configuration can DISABLE it, but on most
> cards, the jumper is the only way of turning it on or off.

This makes the card not a _pure_ EISA card.  If it has resources on it
that respond to I/O cycles that are not controlled by the EISA configuration
parameters, the card is in violation of the EISA spec.

Those cards that use a jumper _only_ to control the ISA floppy interface
on them are not true EISA cards, but mixed ISA/EISA cards.  Seems this is
actually a better thing to do for floppy controllers though :-).

> If you don't realize this, you can wind up with two conflicting floppy
> controllers on the same IRQ, DMA channel, and I/O ports. This can cause
> trouble.

Yepp.... it's just not a pretty picture either way you dice it.  Remeber,
part of the idea of EISA was to eliminate jumper settings and go to a
soft configure, but everyone seems to have cheated on this one :-(.

-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD