On Sat, 25 Jul 2020, Warner Losh wrote:

>       Weren't V5/6/7/etc distributed as bootable tapes?  Set the switch
>       register to point to the tape instead of the disk...
> 
> Yes. They were. We have V6 and V7 tapes (and a V5 disk image). Likely 
> earlier versions likely did too.  What I'd meant was that 2.8BSD is the 
> first 2BSD that had a bootable tape.

Ah, my mistake.

I think the loader also read just the first block, so woe betide you if 
you used a labelled tape...

If I recall, VOL1, HDR1, etc.

-- Dave