Subject: Re: Another changer, another changer problem
To: NetBSD-current Discussion List <>
From: Curt Sampson <>
List: current-users
Date: 10/08/1998 18:19:40
On Thu, 8 Oct 1998, Greg A. Woods wrote:

> Well, I do know about some of the electrical specifications of PCI.
> Unless someone's changed some hardware specs behind my back (and a quick
> review at suggests not), that either means you have at
> least two separate PCI buses in your machine that are separated by a
> bridge, or the mfgr has stretched the limit of the spec and you're not
> likely to have a very reliable machine.

*Shrug*. It works fine for me. Note that even on four-slot motherboards
it's not unusal to have up to six devices (PCI/ISA bridge, Super-IO,
and four slots).

> Ordinary PCI is limited to 4 slots per bus....

Evidently not. At least, ASUS has no trouble producing five-slot
motherboards. See

> ...(and it seems 4 logical units
> per slot, though I don't yet know much about this part of the spec.).

No. A package may have up to eight functions in it.

> Hmm....  You've not been very good at presenting the details of the
> problems you see either....  You wave your hands in objection without
> even really being the Devil's advocate.

I'm going on what little technical information you've given me.
Perhaps, with a detailed presentation, those problems I see won't
really be problems after all because I just don't understand what
you're saying.

> However at this point in the discussion I'm still at the exploratory
> phase, and for something like a revamp of the device configuration
> datastructures into something other than full sized arrays I think we're
> still some distance away from having things concrete enough to even
> build an outline of the design, let alone writing up a detailed paper.

I can't even figure out how you intend to map controllers to the
N in /dev/cN... Perhaps you could explain how this would occur on
typical PCI bus systems.

> > > Perhaps a compile-time flag to select whether or not muliple controllers
> > > per slot is supported or not would help here.
> > 
> > Now we're back to compiling a new kernel again!
> Yes, but only in easily predictable situations.

So? Having more than one SCSI controller in a machine also to my
mind qualifies as an `easily predictable situation.'

Curt Sampson  <>  604-257-9400    De gustibus, aut bene aut nihil.
Any opinions expressed are mine and mine alone.
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