🚀 go-pugleaf

> Then, how on earth does one *put* a boot block on it in the first place? :) 
> Or is this one of those things that you had to buy pre-installed from DEC?

You get a boot block installed by inserting one of the various Pro O/S
installation diskettes into the RX50 floppy drive and booting the machine
(i.e. power it on).  The machine runs software specific to the Pro.

> Also, will an RD53 work on this controller? I've had the same results
> with the RD53 and a couple of assorted disk drives out of PC clones..

The Professional series machines are unique like the Rainbow.

The Pro HD controller would appear to be rather limited, either by ROM
tables on the controller or by the available software.  I vaguely recall
from looking at a service manual the controller has room for up to 1024
cyl and either 4 or 8 heads, I forget (in theory, the registers have the
bits allocated for that ...).

> Btw. I also tried booting an RT-11 floppy from my 11/23+ but "obviously" 
> that didn't work. Which is kind of a bummer... It would have been nice.

The Pro 325/350 may use the F11 chip, but is not a PDP 11/23 (i.e. with
Q-bus devices and standard device addresses etc.) ... memory mapped video,
etc.