On Thu, Aug 30, 2018 at 10:31 AM William Pechter <pechter@gmail.com> wrote:
At least in the old days drives had Write Protect switches.
Not the issue - both disks were RW.  I was running as root and ran a program that lacked a check it shoud have had it (because I was lazy and never put it in there).

Screw IBM for the in cable drive select lines on diskette
You of course realized that was because of field service issues of course.   Setting all floppies (and later ST-506 disks) on the PC and using a twist in the cable meant they did not have to ask FS folks to set the jumpers properly.

and leaving off Write Protect on hard disks.  Some disks had write protect jumpers on the boards...
Hmmm.. I thought all disks at least had a strap.   WD, CDC, Seagate, Shuggart, Toshiba all supported the strap.  The IBM disks I remember did not also, but I'll take your word for it, it would have been like them to have removed it to save the connector cost.

They should have been The STANDARD.
Hmmm.. I'm not at home, but I think I have both the ST-412/506 and ESDI specs in a filing cab somewhere.  I thought the standard did defined it. (Intel blocks 'bitsavers.org' for some reason so I can not look online but I think  http://www.bitsavers.org/pdf/seagate/ST412_OEMmanual_Apr82.pdf is likely to have it in there).