On Tue, 25 Mar 1997, Tom Tarka x3212 wrote:

> the Duo has two SCSI busses.   I was reading through the MkLinux 
> pages today and found Apple's solution for this problem:
> 
> (from http://www.mklinux.apple.com/MkLCurrent/relnotes.html)
> 
> SCSI devices
> 
> For systems that have two SCSI busses (e.g., Power Macintosh 8100s), 
> the two SCSI ID maps are logically merged into one. Devices sharing 
> the same ID, but sitting on separate busses, are not supported. Only 
> the device on the external bus will be accessible in such a case. 

Yeah, and it's one of the more common new user mistakes, because of that. 
I personally didn't agree much with that decision....  Of course, since
NetBSD remaps scsi IDs in order starting with 0 and working its way up,
the problem wouldn't quite surface in that way.  The basic choices under
NetBSD would seem to be: 

alternating internal and external id's (probably a bad idea, too
confusing), e.g.

0i 0e 1i 1e 2i 2e etc.

or

mapping the internal bus first, then the external, e.g.
0i 1i 2i .. 7i 0e 1e 2e etc.

The biggest possible disadvantage to either choice is, if somebody had too
many drives, some would still get lost, but I believe someone told me that
MacOS is basically limited to one busfull of drives, so such a limitation
under NetBSD wouldn't really be that bad.  Knocking out the second SCSI ID
2 would be a Bad Thing (tm) in my opinion. 

Thoughts?

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