SCSI Question (External Drives)

[maceffects]

I have several Macs and some drives will boot as a extra disk (no startup) but when I plug some in the computer trys to boot off it, no matter what I do heck a zip 100 the computer tries to boot off it, even having a scsi cord hooked up to nothing causes blinking question mark. Ideas?

[Dennis Nedry]

If you see an icon in the middle of the screen of a disk with a blinking question mark, that means that the Mac looked all around but it couldn't find any drive that it can start booting from. If you see a smiling Mac icon, that means that it did find a disk that it can boot from. Sometimes if there is a problem, the smiling Mac disappears and goes back to the disk / question mark icon.

You have to have a System Folder on a drive for it to be bootable for your Mac and get the smile icon. We can help you with this if that's the problem.

Please try explaining in more detail exactly what is happening, or even taking pictures, video, etc. We just aren't going to understand the problem based on what you said in the original post.

[maceffects]

The internal he is good and has system installed but most any drive I hook up to the computer it tries to boot off he external drive not the internal. I want a external zip and/or he but when powered it tries to boot off the empty drive.

[Bunsen]

I would have suggested a SCSI ID conflict - make sure the external is set to any ID except 0 or 7 - but this is just weird:

even having a scsi cord hooked up to nothing causes blinking question mark.

Have you tried a different cable?

[Dennis Nedry]

You'll want to first make sure that the internal hard drive is SCSI ID 0, with termination. If it is a different ID, your Mac may not boot form it by default, especially if your PRAM battery is dead.

To set it to ID 0, read the label on the hard drive. If it does not say how to change SCSI ID, use the brand and model number to look up the instructions on the internet.

I think that hooking up just a bare SCSI cable may cause a termination problem, either that or the SCSI cable is bad.

Like Bunsen said, make sure that all of your drives, internal and external, have different SCSI IDs. And also there should be a terminator at the end of your SCSI chain. (The Zip drive has a switch on the back to turn on its terminator.)

[shred]

As Dennis Nedry stated: Double check the ID of the internal drive.

It is surprisingly common to find internal hard drives jumpered incorrectly as ID 6. Why? For some models of Mac, in Australia (and possibly other countries?) Apple charged unrealistically high prices for a Mac fitted with a "factory" hard drive. As such, some dealers would offer the option of a floppy disk only machine plus a third party drive. Most third party drives were jumpered as ID 6 out of the box and some dealers employed inexperienced, incompetent or just lazy technical staff to do this sort of repetitive work.