Date   : Tue, 29 May 2012 20:43:42 +0100
From   : mfirth@... (Michael Firth)
Subject: Setting jumpers SCSI IDs

On 29 May 2012,@17:21, Jules Richardson <jules.richardson99@...>
wrote:

> On 05/25/2012 02:40 PM, Pete Turnbull wrote:
>> On 25/05/2012 10:44, Phill Harvey-Smith wrote:
>>> On 25/05/2012 10:06, Jim Hearne wrote:
>>>>> putting a jumper on makes it a value of '1',
>>>>> and getting it off makes it '0'
>> 
>> Pretty standard for SCSI, especially drives.
>> 
>>> Yes generally SCSI controller/ host adapter has id 7 and drives have ids
>>> 0..6.
>>> 
>>> However if you have an SGI unix box, they decided to have the controller
>>> as id 0 and drives as 1..7 which can be confusing if you are used to
>>> what everyone else uses.....
>> 
>> Actually it would be more accurate to say that most non-PC computer
>> manufacturers use 0 for the controller and 1-7 for the peripherals,
>> which can be confusing if you're only used to PCs :-)
> 
> I think Apple also used #6 for the HBA at one point in time. I'm not sure 
> if they actually supported 8 devices on the bus (inclusive of HBA at #6) or 
> if no device could be placed at ID #7.
> 
I'm pretty sure Apple also used 7 - certainly they had the primary HD as
ID 0. I think they reserved 6 for a CD drive, but I may just be thinking
of Workstation vendors.

Certainly Sun went for this approach - 0 for the first HD, 1 for the second
HD, 6 for the CDROM and 7 for the controller. I think HP workstations had
a similar default setup.

One disadvantage of systems having the controller at 7 is that it ended up
stuck in the middle of the range when things advanced to include wide SCSI,
which has 4-bit IDs instead of 3.

Regards

Michael