Re: SCSI ID vs. unit ID

["Larry \"DrFranken\" Bolhuis" <midrange@xxxxxxxxxxxx>]

Knot to my Knowledge.

They used a sort of inverse SCSI numbering for optical back then. I had 
to decode it when I built Frankie II and Frankie III because we had as 
many as 4 DVD-RAM drives on the same SCSI string. (Get it wrong and IBM 
i think all the drives are the same one!) I believe if you set the 
jumpers for 12 the device became address 3. Something like that anyway.

The tape as you see must be device 0 and has no jumpers installed 
(Unlike Optical). The load source disk then is address 6 and I believe 
that is the only one that mattered. All hard disks needed to be higher 
than that. That thing only accepted 4 drives though given my other 
experiments I do suspect that if you found a way to extend the SCSI 
cable and added a 5th and 6th unit they might function. Just keep 
incrementing the SCSI address.

I think the unit number will more likely match the sequence they were 
added to the machine.

- DrF

On 1/17/2022 8:51 AM, Patrik Schindler wrote:
> Hello,
>
> I'm wondering if there is any mathematical correlation of the SCSI ID of a device on the sole physical SCSI bus of my model 150, and the associated Unit Numbers to be seen in SST.
>
> Device      | ID | Unit
> ------------+----+------
> Load-Source |  6 |  1
> Other Disk  |  5 |  3
> CD-ROM      |  3 |  6
> Tape        |  0 |  5
>
> Can anyone shed some light here?
>
> :wq! PoC