Subject: Re: Another changer, another changer problem
To: NetBSD-current Discussion List <>
From: John Nemeth <>
List: current-users
Date: 10/10/1998 02:12:16
On Oct 3,  9:17pm, Greg A. Woods wrote:
} [ On Sat, October 3, 1998 at 16:11:20 (-0700), John Nemeth wrote: ]
} > } inspection, and by the kernel.  If some patch to your OS causes the
} > } kernel to count from the other direction suddenly then that's something
} > } you do need to be aware of, but it's not generally a problem.
} > 
} >      No, but it blows your whole argument.  If you can't depend on the
} > things to stay put, then why bother using the location as the
} > identifier?
} Does not!
} If you know which way your kernel counts then all you need to do is
} count.  If the kernel suddenly starts counting from the other side then
} you simply count from the other side too.  No magic necessary --
} one-to-one correspondence remains.

     If the name changes for any reason whatsoever, then it can be
considered to be arbitrary.  At that point, it might as well be
something simple instead of something that's ugly and awkward.

} >      As I showed above, the only reasonable and reliable way to handle
} > cards is by the physical slot that it is in.  Having switches of some
} > sort only leads to limitations of how many items of a given kind you
} > can put in the machine and various other conflicts.
} Hmmm... I've never seen much of a problem with using address switches
} and such on VME systems.  Yes VME has timing problems that make it
} difficult to put too many of a certain type of card in, or various types
} of cards too close or too far from the CPU, etc.

     Although, I've administrated VME systems, I haven't had to do
much with the hardware.  Do they let you select from amongst a large
set of addresses, or can certain cards only appear at a small limited
set of addresses?

}-- End of excerpt from Greg A. Woods