> ahc0 at pci2 dev 2 function 0: Adaptec 29160 Ultra160 SCSI adapter
>
> What is the command to tell my U5 to boot on the first scsi disk (SCSI ID 0, part a) ?

You can only boot off adapters that OBP recognizes.  The Adaptec
adapter almost certainly is not recognized (it would need to have
Open Firmware Forth code on board).

Your options are to put the IDE disk back in, to boot off a floppy
(really! :-), or to boot off the net.

A general method to find the recognized disk controllers is the
OBP command "show-disks".  You can then select the controller
you want, and boot off the first disk using "boot ^Y/sd@0,0:a".
The Control-Y will substitute the path to the selected controller.

HTH.


Meilleures salutations -- Volker
-- 
------------------------------------------------------------------------
Volker A. Brandt                  Consulting and Support for Sun Solaris
Brandt & Brandt Computer GmbH              WWW: http://www.bb-c.de/~vab/
Meckenheim, Germany                                   Email: vab@bb-c.de