On Tuesday 15 February 2005 10:02, Eric Siegerman wrote: >On Tue, Feb 15, 2005 at 10:53:55AM +0100, Geert Uytterhoeven wrote: >> I thought[*] 7 was the highest priority, and 0 the lowest (on a >> narrow channel). > >That's what I recall too. > >> Wide devices have an even lower priority: 15 to 8. > >This sounds vaguely familiar too, but I'm *far* less certain >about it.
The bus scan at bootup starts at 0, thats true, but I'm not aware that any device number has a 'higher priority'. As far as the driver scanning the bus to see who yelled when the ATN line gets pulled down, I don't think its done that way at all as the ACK or whatever that comes back then causes the device thats waving its hand to put its address on the bus. So there isn't even a priority there that I know of. If another device also puts up its hand, then I think it gets read for the device number and otherwise queued, and will be serviced as soon as the first device has been told what to do. The scsi bus multitasks very well indeed in well written code. Every device, including the controller, should have collision avoidance built in since thats a basic part of the scsi specs. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) 99.33% setiathome rank, not too shabby for a WV hillbilly Yahoo.com attorneys please note, additions to this message by Gene Heskett are: Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
