allison wrote about the TU58:
For VAX11/750 and 730 users thsi is the microcode boot
device and also
what is used to run diags. So it's important to have a tape or its
analog.
And the HSC50, which is why I'm interested. Though I haven't been able
to obtain an actual HSC50. I've got two HSC70s, but they aren't useful
to me, so I'd be happy to trade one for an HSC50.
Eric