Subject: Re: kern/11627
To: Nathan J. Williams <nathanw@MIT.EDU>
From: gabriel rosenkoetter <firstname.lastname@example.org>
Date: 01/31/2001 16:44:54
On Wed, Jan 31, 2001 at 04:36:02PM -0500, Nathan J. Williams wrote:
> On an i386, there's no such thing. ISA isn't a "real" bus anymore;
> it's simply "that which responds to I/O cycles and possibly memory
> cycles < 16M".
> Even with multiple PCI-ISA cards (a bad idea!), only one of them can
> be programmed as subtractive decode; the other would have to be
> programmed to know about the address ranges of the devices behind
> it, and they'd have to not overlap with the other ISA devices. So
> there's effectively only one ISA bus, regardless of what PCI-ISA
> adapters you plug in.
Glad to admit my ignorance, then. I presumed too much intelligence
in the design of PC hardware. Guess I should know better by now...
(What about PCI-ISA busses in non-i386 machines, then? Do we treat
them the same way? I'm pretty sure such things do exist...)
> (I'm in favor of ripping out "isa* at pcib?" and "isa* at pceb?" and
> just leaving "isa0 at mainbus0", since the former two give the
> not-very-useful impression that the entire ISA bus is behind them.)
Uh... would the ISA bus in this ThinkPad laptop still be detected
properly, then? (It comes up on pcib? right now...)
~ g r @ eclipsed.net