Set the machine into service-mode by hitting one of the buttons on the front.. not sure which one. One of them is 'reset' and the other is 'normal/service'. Once it's in service mode, press CTRL-ENTER while Domain/OS is running or if it's in service mode when you hit reset then it will stop in the PROM and not auto-boot. The PROM mode will look something like this:
MD7C REV 5.00, 1988/10/27.09:18:09
>h
A ACCESS MEM B BRKPOINTS C COPY MEM CA CALL
CB CLR BKPTS D DSPLAY MEM DL DOWN LOAD DP DUMP
OS
DR DUMP REGS DU DUMP SYSTM F FILL MEM G GO
PV PA-TO-VA S SEARCH MEM SS SNGLE STEP V VERIFY
MEM
VP VA-TO-PA XE ENABLE XON XD DISABL XON AR ACC
CTRLRG
DI DEFINE DSK EX EX (CPU) EY EX-N-TRAP FO FORCE LOAD
IC INST CACHE DC DATA CACHE LD LIST SAU LN LIST NETS
LO LOAD FILE M MAP MODE P PHYS MODE RE RESET
SH SHUT DISK SK SEL KEYBD TE TEST H HELP
(note, the commands will be different because that's the output from
one of my Apollo 3500's).
You should be able to type "CF" I believe to configure either DOMAIN or HPUX mode. Once in HPUX mode, it will be able to boot NetBSD though the Domain keyboard should still work in both modes from the PROM. But no further.
Alternatively, there are ways to break into Domain/OS if you felt that was necessary. shouldn't be though.
Press <space> to enter System Search Mode. Once you see `System Search
Mode' at the bottom of your screen, press <c> <return> to enter Configuration Mode. You'll be presented with a list of configurable interfaces, one of which will be RS-232 at Select Code 9. This menu will be in the upper-right corner of your screen.
Select the RS-232 at Select Code 9 option (menu item 2 on my 380, but your mileage may vary). There will be several configurable options for this (which, incidentally, is the on-board `dca'). Look for the `Remote/Local' option. It's probably set at `L'. To make the system use the dca as the console, set this to `R'. Once you've set the Remote flag, type <x> <return> to get back to the main menu, and then type <n> <return>. This will cause the machine to save the new values in the EEPROM and reset. You'll want to have a terminal plugged in to the dca at this point.
If, for some reason, you goof up and lose the video console and need to get it back, the bootrom will usually prompt you to hit `L' at boot time to use the `Local Console' (video) ... It's worked for me before in the bootrom, but once an OS (HP-UX or NetBSD) started, it looked at how the various ports were configured. But, it's enough to switch the console back if you have to.
> Well, during self-check you can just tap the spacebar to bing up a list of
> boot choices, and can select via a menu. On some systems, you can
> `save' this choice in the EEPROM. On my 319 (with a Rev C1 ROM, I
> believe), I have no disks attached, and it just defaults to the LAN device.