PDP Prompt?

[Tim Shoppa]

> I'm trying to revive a PDP 11/04, but not having much luck at the moment..
> I got a serial terminal hooked up to it, and upon bootup, it gives me the
> following on the display:
> 
> <triangle sign><triangle sign> 177777 177776
> $
> 
> apparently, $ is some sort of a prompt. It only accepts two characters,
> and after, it seems, any pair of characters, will go on and give me a new
> prompt.
> 
> Is this some sort of a ROM debugger? What can I tell it? I think I've
> tried almost every combination of 2 letters without any success..

Commands available at this prompt include:

L<space>nnnnnn<CR> - to set an address
E<space>           - to examine the address set with L
D<space>nnnnnn<CR> - to deposit at an address set with L
S<CR>	           - begin running at the loaded address

The console ROM is very picky; all letters need to be in upper case,
and you need to type <space> and <CR> in exactly the right places.
It's also very stupid, in that if you try to Examine or Deposit to
a non-existent address, the only clue you get is that the RUN light on
the goes out and you have restart it from the front.

> It's a 11/04, with a dual 8" floppy drive and some big cage made by MTS,
> with nothing in it but a large number of slots. Has some buttons saying
> 'STATION 1 DUMP', 'STATION 2 DUMP', and so on.. The floppy drive has two
> 8" floppies in it, one of them appears to be some sort of a system floppy,
> the other has no label.
> 
> Does this look like even remotely salvageable? :)

It'll never run a modernish Unix, but it will run RT-11 just fine.

Is the floppy controller a DEC RX211 (M8256) or RX11 (M7846) or some
third-party clone?  Are there any boot ROM's on the M9312?  The RX01
boot ROM is 23-753A9, and the RX02 boot rom is 23-811A9.  If you've
got a third party RX clone controller, it may have the boot ROM on that
board.  Try examining addresses 173000, 173200, 173400, 173600, and
171000 to see if a boot ROM might be living at any of these addresses.

As this is very non-Unix related, you might want to ask any other questions
you have on a more general PDP-11 related forum, such as the Usenet newsgroup
"vmsnet.pdp-11".

Tim. (shoppa at triumf.ca)

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