Wont Boot From Second Drive

From: Dominique Petitpierre <petitp@divsun.unige.ch> Subject: Mac won't boot from second disk. Why? Here is the summary of the answers I got for the question I asked on December 18th in Info-Mac Volume 13 Issue 176: |I have just added a second internal disk drive in my Macintosh, and would |like to make it the boot disk while keeping the old disk still bootable in |case of problems. Infortunately, whatever I do, the Mac insists to boot |from the old disk. |- Why? What can I do? The short answer: ================= What worked for my purpose was to exchange the SCSI ids of the disks, putting the new disk at target 0, and the old target 0 disk at target 1. Now I can use Startup Disk to choose whichever of these two disks as boot disk, and at the next restart the mac boots from the chosen disk. The reason it works has to do with the fact that the Mac tries longer to boot from SCSI target 0. Many thanks to Julian Daniel, North Star Computer Ltd. <norstar@bconnex.net> who suggested this. If my purpose is fullfilled, the real problem is not solved: How can you force the Mac to wait long enough for disks not at SCSI target 0. For example I have another old external disk, that I use only briefly for backups because it is too noisy. The same symptom occurs: even if it is bootable when it is the only disk on the SCSI bus, the Mac won't boot from it if the internal disk is available, whatever I do. Thanks to all the people who helped with suggestions: Julian Daniel <norstar@bconnex.net> Jim Carr <Jim.Carr@latimes.com> Christian F. Buser <cbuser@access.ch> Gregory Johnson <gregj@desktopdesign.com> Glenn Schaffer <Gschaffe@michp7.redstone.army.mil> Thomas Ytterberg <thomas.ytterberg@mailbox.swipnet.se> Dr. Francisco-J. Renero-C. <paco@xochitl.inaoep.mx> Art Treiber <artt@mail.erols.com> The long answer: ================ For the curious, here is a summary of other suggestions I received with comments and of a few things I discovered while trying to solve this. First here are the informations I provided with my original question: |Here are some facts and things I tried: | |My setup: |Computer: MacIIx with System 7.0.1 and Tune Up 1.1.1 (on the old disk). |Old disk is a Quantum 170S at SCSI target 0 with driver FWB HDT (I never |touched this, and would prefer not to). |New disk is an IBM DPES 31080 at SCSI target 3 with Silverlining 5.4.2/16 |(also tried 5.6.3/25) |The new disk has a bare fresh system 7.0.1, installed from the Apple System |7.0.1 diskettes. |The "Startup Disk" control panel shows the new disk selected as startup disk. | |Tests and observations: |- The System Folder on the new disk is blessed (shows the icon). |- After boot on the old disk, the new disk mounts fine (appears on | the desktop). |- If the old disk is disabled (physically disconnected), the new disk boots | fine (so it IS bootable). |- At boot time, I hear that the new disk is probed twice: once before boot | starts on the old disk and once after. With Silverlinin…