[jan-jaap]

I took the disk out of the drive tower module. Initially it didn't even spin up, but I managed to unstick it by jolting it in the rotational direction of the platters and letting inertia do it's thing. it spins up now, but then it makes a "dakdakdakdakdakdakdakdakdakdakdakdak" noise that it doesn't seem to get out of.

I guess the degaussing has successfully destroyed this hard disk beyond recovery?

You could attach it to a working machine and send a TEST UNIT READY command (this is the SCSI command consisting of six zero bytes {0,0,0,0,0,0}), the status will tell if it is capable of being reformatted.
One way would be to run scsicontrol -Dd /dev/scsi/scXXXXX

I gave this a try, but the doesn't show up anywhere on the bus. I know being a system disk it is jumpered for ID #1. No clever tricks on the Professional IRIS: it's set on the device.

• In an Octane, using a CR-ROM enclosure to power and connect the disk to the system, it doesn't show up in 'hinv' and no device is created under /dev/scsi
  
• I attached the same assembly to a Linux PC with an Adaptec 2940UW card and it doesn't probe a device either
  
• Finally, to rule out the possibility that the CD-ROM enclosure doesn't supply enough power, or that the ultra-wide SCSI buses might not like this very early SCSI disk, I mounted it in a 4D disk bracket and tried with the Crimson. Again, it doesn't show in 'hinv'. IRIX 6.2 has static enties under /dev/scsi for every possible device, but an attempt to open (1,1) with scsicontrol resulted in a 'can't open'.
  

All I can say is that the endless clattering of the head momentarily stops when the SCSI bus is probed by the host, at boot or reboot