>When the machine first comes up, SHOW DEVICE reports the drive as an
>RD51.  After several resets, it finally decides that it's an RD54.

This usually indicates that the RD54 is on its last legs.  The RQDX3
on initialization goes out and queries all the connected hard drives
by reading the formatting info on them.  If it can't recognize the
drive for one reason or another, it gets categorized as a RD51.

>Is this normal?  Or is something broken?

It probably means that your RD54 is dying.  (No surprise there!)
It's possible that a reformat would help eek a few more months of life
out of it.

>Is there a console command I can give that will cuase the system to
>not attempt to autoboot?  Right now I've got that by giving it a
>SET BOOT with a bogus device name, but surely there's a better way.

The cab kit for the CPU has two switches with three positions on them.
You obviously haven't looked at the OpenVMS FAQ where the switch
positions are explained, so here's the information from
www.openvms.digital.com:

The MicroVAX-series console bulkhead was used with the KA630, KA650,
KA655 processors. 

There are three controls on the console bulkhead of these systems: 
 Triangle-in-circle-paddle:  
                       halt enable.
 dot-in-circle: 
   
                       halt (BREAK) is enabled,
                       and auto-boot is disabled. 
 dot-not-in-circle: 
   
                       halt (BREAK) is disabled,
                       and auto-boot is enabled. 


 Three-position-rotary:  
                    power-up bootstrap behaviour
 arrow:  
                    normal operation.
 face:  
                    language inquiry mode.
 t-in-circle:  
                    infinite self-test loop.


 Eight-position-rotary:   
   
                   console baud rate selection
                   select the required baud rate; read at power-up.


Those versions of the console bulkhead that do not have an MMJ have a
9-pin submini connector (DB9), and the pinout of this connector
predates the PC 9-pin pinout - the console pinout is consistent with
the EIA232 pinout. See MISC4 for details of the DB9 pinout. For those
bulkheads not equipped with an MMJ, use the H8575-B adapter to convert
the console connector to MMJ. See MISC1 for further details. 

Also present on the bulkhead is a self-test indicator: a single digit.
This matches the final part of the countdown displayed on the console
or workstation, and can be used by a service organization to determine
the nature of a processor problem. The particular countdown sequence
varies by processor type, consult the hardware or owner's manual for
the processor, or contact the local hardware service organization for
information the self-test sequence for a particular processor module.
Note that self-tests 2, 1 and 0 are associated with the transfer of
control from the console program to the booting operating system. 

>Is there a way to abort an attempted boot?  When I first fired up the
>box, it was always trying to boot from XQA0, and I had a difficult time
>getting a command prompt.  I'd hoped that the halt switch on the front
>panel would do that, but it seemed to only make it run the power-up
>diagnostics in a loop.

This indicates that you've got the first switch set to "dot not in
circle", i.e. halt disabled. 

>If I add more drives, do I need to install more front-panel inserts for
>them?

If you want the drive to be on-line and write-enabled at all times, then
you don't need it.

>Can a BA123 handle three RD54s, a TK50, and an RX50?

It depends on what else you've got connected to the BA123 power supplies.
The system originally came with a worksheet showing the power draw of
all the devices in it as well as the maximum available from each
power supply.  You probably don't have this worksheet, but you ought
to do the calculation for your system if you really want to fully deck
it out.

Questions like yours are answered in the DECUServe collection
"THIRD-PARTY-DISKS.TXT" available at ftp://ftp.spc.edu/ and other
places.  (Why isn't this resource mentioned more prominently on
the NetBSD pages?  It answers a good fraction of the questions
commonly asked here...)

-- 
 Tim Shoppa                        Email: shoppa@trailing-edge.com
 Trailing Edge Technology          WWW:   http://www.trailing-edge.com/
 7328 Bradley Blvd		   Voice: 301-767-5917
 Bethesda, MD, USA 20817           Fax:   301-767-5927