Subject: Re: Put home directories on second hard drive?
From: Gordon Neault (gordo-x@shaw.ca)
Date: Sat Dec 22 2001 - 16:13:18 MST
Okay, I am not a "real" expert on SCSI, but I can tell you the following:
SCSI devices have an ID number assigned to them. Each number must be
unique, although it doesn't have to follow any particular order. For
example, you could have devices with ID 1,3, and 6 on a chain and they
can be hooked up in any order (6 first, then 1, then 3 is OK).
Here is some info:
You cannot use ID 7; this is reserved for the Mac itself.
Apple assigns the original HD a device ID of 0.
Apple assigns the CD drive a device ID of 3.
Apple recommends a higher number to devices you use most frequently,
although there is very little to document exactly why and I understand
millions of Mac users don't bother.
Launch Apple System Profiler to learn details of your SCSI chain (device
ID, etc). You can also use a freeware/shareware utility called SCSI
Probe.
Update all drivers on your SCSI devices.
You may have to do this with one drive installed (boot from CD) and then
the other (boot from CD). If one drive will not boot when only it and
the CD are installed, I would try removing the CD cable and running with
both HDs only. (This is a clue that one HD has ID 3). You will need a
system folder on one HD.
There is such a thing as a drive with only one ID number but it is rare.
Generally you will find a slide switch (choice of 2 pre-assigned ID
numbers) or a PCB style rotary switch (the best, choice of all available
IDs). These switches requires a small screwdriver or pen tip to change
the ID numbers.
Some drives have internal termination, and sometimes you can switch it
off and on. You should have termination enabled on the last drive in the
chain.
If there is no internal termination, a plug-in terminator is required.
This is a thingy with a SCSI port on one end and nothing on the other (a
plug that you can't plug anything else into).
If you don't have a terminator (ie one wasn't installed on the CD when
you first opened the case) then it is likely the CD has an internal
terminator. Make it the last device on your chain and you should be OK.
SCSI cable quality is often cited as a failure point; you may end up
buying one if all else fails.
On Saturday, December 22, 2001, at 02:41 PM, Zeke Runyon wrote:
>
> On Saturday, December 22, 2001, at 01:45 PM, Gordon Neault wrote:
>
>> I'm sure someone has pointed it out, but does each HD (the "existing
>> drive" and the "new drive") have a unique SCSI ID?
>
> I don't know. How do I find out/change the SCSI IDs?
>
>> Does your Mac have an internal terminator for the SCSI chain and is it
>> connected to the last drive in the chain? If not, is the last drive
>> terminated?
>
> Terminated? huh?
>
>> Could what you call "a connector at the end of the chain" be a
>> terminator?
>
> All I know is that it is a long black connecter at the end of the chain
> that fits in the second HD.
>
> ##
> # Zeke Runyon | zrunyon@mac.com | zekeworld.home.dhs.org
> # blog: communistsquirrel.home.dhs.org
> # Mac OS X 10.1.1 5M28 | OS 9.2.1 | Yellow Dog Linux 2.1
> # Communist squirrels shall rule the world.
>
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