Re: HP 21MX paper tapes

2016-03-07 Thread Mattis Lind
2016-03-08 4:56 GMT+01:00 J. David Bryan :

> On Monday, March 7, 2016 at 22:14, Mattis Lind wrote:
>
> > I have been going to our HP 21MX paper tapes that come with a M-series
> > system that we received many years ago:
> >
> > http://www.datormuseum.se/documentation-software/hp-paper-tapes
> >
> > I tried to check if they already were available online somewhere but
> > didn't find them
>
> The HP 1000 Software Collection at Bitsavers has a numerical list of all of
> the tape images that are archived.  It's under:
>
>   /bits/HP/HP_1000_software_collection/master-files/
>
> Please check your list against the "master-files-list.txt" file, which
> lists all of the files in the collection.  But first, please check against
> "master-bad-files-list.txt", which are the files in the collection that are
> damaged.  If you have good copies any of the damaged files, or of any files
> that are not in the full list, they would be welcome additions.
>


Thanks for the pointer to the master-files-list.txt. While lists I found a
few that weren't present in that list:

24151-60001 DRTE/DOS RELOCATEABLE LIBRARY-F2E (EAU) BINARY
24152-60001 CRTE/DOS FORTRAN IV LIBRARY R BINARY
24156-60001   1419   DOS DVR31 FOR 2870/7900/7901 DISC BINARY

But these files I found listed in
/bits/HP/paperTapes/JeffM/old_index.html.txt

So it seems that all of them are stored online somehow!

/Mattis





>   -- Dave
>
>


Release of the HP 3000 Series III simulator

2016-03-07 Thread J. David Bryan
I am pleased to announce the release of a simulator for the HP 3000 Series 
III computer system.  It is available from the Computer History Simulation 
Project (SIMH) site:

  https://github.com/simh/simh

The simulator runs the MPE-V/R operating system, supports a selection of 
simulated disc and tape drives, and accommodates up to sixteen concurrent 
users.  A software kit containing a disc image with MPE preinstalled is 
available as described in the release notes that accompany the simulator.

I would like to thank Frank McConnell and Al Kossow for their invaluable 
help in answering questions and supplying documentation for the HP 3000.

  -- Dave



Re: Cables

2016-03-07 Thread Paul Anderson
I found my programmers panel, but none have cables.Do you have the DEC part
number?

On Thu, Mar 3, 2016 at 11:03 AM, Jon Elson  wrote:

> On 03/03/2016 12:52 AM, jwsmobile wrote:
>
>> Anyone have a source for IDC cables / supplies?  I'm in need of some 40,
>> 50 and various other cables and connectors.
>>
>> I need some specifically for dec systems so those would be even better.
>>
>> The most urgent need is cables for the PDP 8/A front panel cabling. They
>> are all 40 pin.  I've got a unit with the programmers panel, so need cables
>> for it and for the basic power panel.
>>
>> Generally, you can make the 40-pin DEC cables yourself.  All you need is
> cable, the connectors and a vise.
> I do these all the time.  (Harder is the DEC proprietary printed ribbon
> cables.)
>
> Jon
>


Re: HP 21MX paper tapes

2016-03-07 Thread J. David Bryan
On Monday, March 7, 2016 at 22:14, Mattis Lind wrote:

> I have been going to our HP 21MX paper tapes that come with a M-series
> system that we received many years ago:
> 
> http://www.datormuseum.se/documentation-software/hp-paper-tapes
> 
> I tried to check if they already were available online somewhere but
> didn't find them 

The HP 1000 Software Collection at Bitsavers has a numerical list of all of 
the tape images that are archived.  It's under:

  /bits/HP/HP_1000_software_collection/master-files/

Please check your list against the "master-files-list.txt" file, which 
lists all of the files in the collection.  But first, please check against 
"master-bad-files-list.txt", which are the files in the collection that are 
damaged.  If you have good copies any of the damaged files, or of any files 
that are not in the full list, they would be welcome additions.

  -- Dave



RE: MEM11A questions

2016-03-07 Thread Jay West

Mike wrote...
-
Ah ok so it's a universal RAM board that will add modern reliable Unibus memory 
to any -11 from the 11/20 on up?

I'll have six please! Preferably tomorrow!


All comes down to what I can afford, how much that detracts funds from purchase 
of the "newer version" that does disk storage as well

But I'd tentatively say I'd want 2 of 'em.

J




Re: HP 21MX paper tapes

2016-03-07 Thread Al Kossow

They would be part of the cupertino binary distribution tapes on bitsavers.
Unlike DEC, HP had part numbers for EVERY program, with date-coded 
revisions.



On 3/7/16 1:14 PM, Mattis Lind wrote:

I have been going to our HP 21MX paper tapes that come with a M-series
system that we received many years ago:

http://www.datormuseum.se/documentation-software/hp-paper-tapes

I tried to check if they already were available online somewhere but didn't
find them





OT: domain for sale

2016-03-07 Thread Evan Koblentz
Is anyone interested in buying technologyrewind.com? It would be a good 
name for a collector's site.


Re: MEM11A questions

2016-03-07 Thread Guy Sotomayor

> On Mar 7, 2016, at 2:06 PM, Mike Ross  wrote:
> 
> On Tue, Mar 8, 2016 at 10:46 AM, Guy Sotomayor  wrote:
>> 
>>> On Mar 7, 2016, at 1:27 PM, Mike Ross  wrote:
>>> 
>>> On Tue, Mar 8, 2016 at 8:16 AM, Guy Sotomayor  wrote:
 Hi,
 
 Over the weekend I was looking through some old CAD files and came across 
 my
 original design for the MEM11A.  It was an SPC board that contained only 
 128KW
 of FRAM.
 
 I’m wondering if there’s any interest in that board.  I do have to iterate 
 on the design
 a bit but I should be able to get something ready sooner than with my 
 current board
 design (plus I know it will fit in an SPC form factor because I’ve already 
 done it).
 
 What I’d like to know from folks is if there’s interest in that design?  
 Would there still
 be interest in what I’m now calling UMF11 (Unibus Multi-Function)?
>>> 
>>> Ummm enlighten us a little more about what exactly it could do and
>>> what machines it could be used in?
>> 
>> MEM11A?  It can be used in any PDP11 that has SPC slots and will provide 
>> 128KW
>> of non-volatile RAM.  I had originally gone down this road to provide memory 
>> for
>> memory challenged machines (most notably the 11/20) but could be used in any
>> Unibus PDP11.
> 
> Ah ok so it's a universal RAM board that will add modern reliable
> Unibus memory to any -11 from the 11/20 on up?
> 
> I'll have six please! Preferably tomorrow! (It was the 'multifunction'
> bit that confused me; I wondered if it was doing something else beyond
> memory)
> 
> 

OK, part of this is my own fault.  I started working on a board design (MEM11A) 
that
was only memory.  During one of the (several) re-designs it morphed into the 
multi-funciton
board that I’ve also been calling MEM11A.

To alleviate the confusion as I’m thinking of resurrecting the *original* 
MEM11A design
(just Unibus Memory), I’m renaming the more recent design (which I also called 
MEM11A)
to UMF11 (Unibus Multi-Function) which has in addition to memory, DL11s, 
RF11/RS11s,
etc to be able to support all of the peripherals (sans RK11) needed for Unix V1.

So to re-iterate, I’m looking at producing two products:
MEM11A which is just 128KW of memory in an SPC form factor
UMF11 which is 128KW of memory, 2 DL11s, RF11/RS11s, boot roms, etc.

The UMF11 has been taking so long because it has a micro-controller (J1) on it 
to perform
the configuration and emulation tasks.  It has no switches and only a few 
jumpers.  Every
thing else is configured through one of the serial ports.

I’ve finished the Verilog code for the UMF11 and am close to completing the 
simulation of
all of the individual blocks.  I still have some uCode work to do in terms of 
emulated
devices but now that all of the H/W interfaces are designed and coded, I can 
complete
that as well.  The remainder is doing the schematic capture, board layout and 
testing…lots
and lots of testing.  ;-)

The MEM11A is *much* simpler and the work I need to do on it is mainly to put 
the random
logic into a CPLD.  In that respect, the MEM11A is pretty hardwired compared to 
the UMF11.

TTFN - Guy



Re: MEM11A questions

2016-03-07 Thread Mike Ross
On Tue, Mar 8, 2016 at 10:46 AM, Guy Sotomayor  wrote:
>
>> On Mar 7, 2016, at 1:27 PM, Mike Ross  wrote:
>>
>> On Tue, Mar 8, 2016 at 8:16 AM, Guy Sotomayor  wrote:
>>> Hi,
>>>
>>> Over the weekend I was looking through some old CAD files and came across my
>>> original design for the MEM11A.  It was an SPC board that contained only 
>>> 128KW
>>> of FRAM.
>>>
>>> I’m wondering if there’s any interest in that board.  I do have to iterate 
>>> on the design
>>> a bit but I should be able to get something ready sooner than with my 
>>> current board
>>> design (plus I know it will fit in an SPC form factor because I’ve already 
>>> done it).
>>>
>>> What I’d like to know from folks is if there’s interest in that design?  
>>> Would there still
>>> be interest in what I’m now calling UMF11 (Unibus Multi-Function)?
>>
>> Ummm enlighten us a little more about what exactly it could do and
>> what machines it could be used in?
>
> MEM11A?  It can be used in any PDP11 that has SPC slots and will provide 128KW
> of non-volatile RAM.  I had originally gone down this road to provide memory 
> for
> memory challenged machines (most notably the 11/20) but could be used in any
> Unibus PDP11.

Ah ok so it's a universal RAM board that will add modern reliable
Unibus memory to any -11 from the 11/20 on up?

I'll have six please! Preferably tomorrow! (It was the 'multifunction'
bit that confused me; I wondered if it was doing something else beyond
memory)

Mike

http://www.corestore.org
'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'


Re: MEM11A questions

2016-03-07 Thread Guy Sotomayor

> On Mar 7, 2016, at 1:27 PM, Mike Ross  wrote:
> 
> On Tue, Mar 8, 2016 at 8:16 AM, Guy Sotomayor  wrote:
>> Hi,
>> 
>> Over the weekend I was looking through some old CAD files and came across my
>> original design for the MEM11A.  It was an SPC board that contained only 
>> 128KW
>> of FRAM.
>> 
>> I’m wondering if there’s any interest in that board.  I do have to iterate 
>> on the design
>> a bit but I should be able to get something ready sooner than with my 
>> current board
>> design (plus I know it will fit in an SPC form factor because I’ve already 
>> done it).
>> 
>> What I’d like to know from folks is if there’s interest in that design?  
>> Would there still
>> be interest in what I’m now calling UMF11 (Unibus Multi-Function)?
> 
> Ummm enlighten us a little more about what exactly it could do and
> what machines it could be used in?

MEM11A?  It can be used in any PDP11 that has SPC slots and will provide 128KW
of non-volatile RAM.  I had originally gone down this road to provide memory for
memory challenged machines (most notably the 11/20) but could be used in any
Unibus PDP11.

TTFN - Guy



Re: MEM11A questions

2016-03-07 Thread Mike Ross
On Tue, Mar 8, 2016 at 8:16 AM, Guy Sotomayor  wrote:
> Hi,
>
> Over the weekend I was looking through some old CAD files and came across my
> original design for the MEM11A.  It was an SPC board that contained only 128KW
> of FRAM.
>
> I’m wondering if there’s any interest in that board.  I do have to iterate on 
> the design
> a bit but I should be able to get something ready sooner than with my current 
> board
> design (plus I know it will fit in an SPC form factor because I’ve already 
> done it).
>
> What I’d like to know from folks is if there’s interest in that design?  
> Would there still
> be interest in what I’m now calling UMF11 (Unibus Multi-Function)?

Ummm enlighten us a little more about what exactly it could do and
what machines it could be used in?

Thanks

Mike

http://www.corestore.org
'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'


HP 21MX paper tapes

2016-03-07 Thread Mattis Lind
I have been going to our HP 21MX paper tapes that come with a M-series
system that we received many years ago:

http://www.datormuseum.se/documentation-software/hp-paper-tapes

I tried to check if they already were available online somewhere but didn't
find them when doing quick checks on random tape part numbers in the spread
sheet. Maybe they are and then I don't need to bother reading them.
Otherwise I will try to read them if there are interest and when I get time.

/Mattis


Re: 11/23+ box with Microvax Memory

2016-03-07 Thread Pete Turnbull

On 07/03/2016 18:25, jwsmobile wrote:

I see on the usual site, an 11/23 box with a couple of random boards,
one of which is an M7608 board.  This is a Microvax memory board.

I wonder if one can build up a Microvax in that backplane, or if that is
not recommended.  It would obviously be an 18 bit backplane.  The
backplane is H9276A.


That's a 22-bit backplane so I don't see why you couldn't build a 
microVAX in it.  Bear in mind it's all straight QQ-CD, unlike BA23 and 
BA123 backplanes normally used for microVAXen, which have serpentine 
sections and can hold more cards.


--
Pete


RE: tops20 assembly tutorials

2016-03-07 Thread Rich Alderson
From: David Griffith
Sent: Saturday, March 05, 2016 9:36 PM

> Would someone please point me towards a tutorial of some sort on running 
> the assembler on TOPS20 as presented in Mark Crispin's Panda distribution?

http://www.bitsavers.org/pdf/dec/pdp10/TOPS20/AA-4159C-TM_Macro_Assembler_Reference_Apr78.pdf

http://www.bitsavers.org/pdf/dec/pdp10/TOPS20/DEC-20-OMUGA-A-D_Monitor_Calls_Users_Guide_May76.pdf

If you are comfortable with assembler language programming, these should
suffice.  If not, there are pointers to one online textbook in the recent
flurry of messages discussing the Gorin textbook; besides the TOPS-20 books
there is the Singer DEC-10 assembler book (monitor calls differ immensely
from TOPS-20, so of limited use for you).  The following are the most recent
system calls manuals, but as text files they're actually harder to read till
you're used to the format from the older version of the user's guide above.

http://www.bitsavers.org/pdf/dec/pdp10/TOPS20/V7/JSYS_USERS.MEM.txt

http://www.bitsavers.org/pdf/dec/pdp10/TOPS20/V7/JSYS_REFERENCE.MEM.txt

(Oh.  TOPS-20 monitor calls are referred to as "JSYS calls", since that is
 the machine instruction, opcode 104, which invokes them.  Thus these names.)

Once you have a basic grasp of the assembler from the above, I recommend
perusing the sources to the MM mail manager suite of programs, which use
very good programming style, including the "structured programming" macros
found in MACSYM.MAC.  Ralph did not think highly of them, and used an older
style in which conditional code is included in literals; the textbooks all
seem to utilize that style.

Wait.  You said "running the assembler".  Did you mean, "How do I invoke
Macro-20?"  That's simple:  The commands COMPILE, LOAD, EXECUTE, and DEBUG
all recognize the file type .MAC as requiring Macro-20 and do the Right
Thing(TM) automagically.  If you need more than that, the Macro-20 manual
above and the LINK manual (damn it, there's not a copy on Bitsavers--talk
to me, Al!) will provide details of how to invoke them.

COMPILE does only that.  LOAD will compile if necessary and link the result
into an executable image in memory (which can be saved as an executable
program file with the SAVE command).  EXECUTE and DEBUG will compile if
needed, link, and respectively either simply start running or invoke DDT
and leave you ready to execute, examine memory, etc.

Do you need a pointer to the user commands manual?

http://www.bitsavers.org/pdf/dec/pdp10/TOPS20/V7/USERS.MEM.txt

Rich


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:ri...@livingcomputermuseum.org

http://www.LivingComputerMuseum.org/


Re: 11/23+ box with Microvax Memory

2016-03-07 Thread Glen Slick
On Mon, Mar 7, 2016 at 10:25 AM, jwsmobile  wrote:
> I see on the usual site, an 11/23 box with a couple of random boards, one of
> which is an M7608 board.  This is a Microvax memory board.
>
> I wonder if one can build up a Microvax in that backplane, or if that is not
> recommended.  It would obviously be an 18 bit backplane.  The backplane is
> H9276A.
>
> The auction also has a M9047 Bus grant card in it, so is essentially just
> the box.  But I'd never seen Microvax parts plugged into those backplanes,
> and it made me think.

The H9273 is a 9 row Q18/CD backplane and the H9276 is a 9 row Q22/CD
backplane. I don't see why you couldn't build up a QBus MicroVAX in an
H9276 backplane. You'd have to hack up something to mount the console
bulkhead panel in a BA11 box instead of the standard BA23 box.


Re: Passing of Ray Tomlinson

2016-03-07 Thread Adrian Stoness
Was all over the CBC today up here in Canada this morning or least in wpg
On Mar 7, 2016 11:21 AM, "Murray McCullough" 
wrote:

> We communicate today, as yesterday, via email. Ray Tomlinson,a 1960's
> ARPAnet pioneer has passed on. He 'invented' the @ symbol. My how old
> things are truly great.
>
> Murray  :)
>


11/23+ box with Microvax Memory

2016-03-07 Thread jwsmobile
I see on the usual site, an 11/23 box with a couple of random boards, 
one of which is an M7608 board.  This is a Microvax memory board.


I wonder if one can build up a Microvax in that backplane, or if that is 
not recommended.  It would obviously be an 18 bit backplane.  The 
backplane is H9276A.


The auction also has a M9047 Bus grant card in it, so is essentially 
just the box.  But I'd never seen Microvax parts plugged into those 
backplanes, and it made me think.


thanks
Jim


Passing of Ray Tomlinson

2016-03-07 Thread Murray McCullough
We communicate today, as yesterday, via email. Ray Tomlinson,a 1960's
ARPAnet pioneer has passed on. He 'invented' the @ symbol. My how old
things are truly great.

Murray  :)


Re: SeaMonkey - Re: Usenet News Servers

2016-03-07 Thread Liam Proven
On 6 March 2016 at 21:33, Dave Wade  wrote:
> SeaMonkey is essentially the same code as in Thunderbird/Firefox. Personally
> I prefer to keep browser and mail/news separate. Pretty sure it will import
> from the old Netscape Communicator.


It appears that Jerome has killfiled me, as I have answered this
question for him at considerable length several times. Perhaps someone
would like to forward my old messages to him.

-- 
Liam Proven • Profile: http://lproven.livejournal.com/profile
Email: lpro...@cix.co.uk • GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lpro...@hotmail.com • Skype/AIM/Yahoo/LinkedIn: liamproven
Cell/Mobiles: +44 7939-087884 (UK) • +420 702 829 053 (ČR)


Re: I want a front panel for my lsi 11 w/switches and lights

2016-03-07 Thread Richard Cini
Thanks Bill. I use PDP11GUI for loading the TU58 boot loader into my H11. It's 
a great program. I just thought I missed a glitzy feature!

Rich

Sent from my iPhone

> On Mar 7, 2016, at 9:14 AM, william degnan  wrote:
> 
>> On Mon, Mar 7, 2016 at 8:58 AM, Richard Cini  wrote:
>> 
>> Does PDP11GUI have blinkenlights? I use GUI for my Heath H11 and it works
>> great but I do like blinkenlights.
>> 
>> Rich
>> 
>> 
>> Sent from my iPhone
> No, it's a monitor program, here is an example of me loading an echo
> characters program into the computer using from PDP11GUI as the interface.
> 
> http://vintagecomputer.net/digital/PDP11-40/Console_test.jpg
> 
> -- 
> @ BillDeg:
> Web: vintagecomputer.net
> Twitter: @billdeg 
> Youtube: @billdeg 
> Unauthorized Bio 


Re: I want a front panel for my lsi 11 w/switches and lights

2016-03-07 Thread william degnan
On Mon, Mar 7, 2016 at 8:58 AM, Richard Cini  wrote:

> Does PDP11GUI have blinkenlights? I use GUI for my Heath H11 and it works
> great but I do like blinkenlights.
>
> Rich
>
>
> Sent from my iPhone
>
>
>
No, it's a monitor program, here is an example of me loading an echo
characters program into the computer using from PDP11GUI as the interface.

http://vintagecomputer.net/digital/PDP11-40/Console_test.jpg

-- 
@ BillDeg:
Web: vintagecomputer.net
Twitter: @billdeg 
Youtube: @billdeg 
Unauthorized Bio 


Re: I want a front panel for my lsi 11 w/switches and lights

2016-03-07 Thread Richard Cini
Does PDP11GUI have blinkenlights? I use GUI for my Heath H11 and it works great 
but I do like blinkenlights.

Rich


Sent from my iPhone

> On Mar 7, 2016, at 8:30 AM, Paul Birkel  wrote:
> 
> Sounds like PDP11GUI ... with the glass-interface supplemented by a
> mechanical one?
> 
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Noel
> Chiappa
> Sent: Monday, March 07, 2016 7:41 AM
> To: cctalk@classiccmp.org
> Cc: j...@mercury.lcs.mit.edu
> Subject: Re: I want a front panel for my lsi 11 w/switches and lights
> 
>> From: Ed Sharpe
> 
>> I want a front panel  for  my lsi 11  w/switches and  lights!
> 
> That's going to be a little tricky. The LSI11 obvously doesn't have a
> hardware interface on/in the CPU which would allow a lot of the functions
> traditionally found in a front panel (e.g. examining registers, single step,
> etc).
> 
> Some of them can be done (e.g. a halt/run switch, which LSI-11's already
> support), and others could be 'sorta' done - e.g. if the CPU is running, DMA
> could be used to read/write memory locations.
> 
> Probably the best way to have an emulated front panel is to build a board
> that i) emulates the system serial console on the QBUS (i.e. responds to
> 177560-6), and ii) has a micro or something which uses ODT to emulate the
> full range of normal console commands, and drives a set of LEDs and
> switches.
> 
> E.g. hitting the 'continue' switch when the processor was halted would issue
> a 'P' command to ODT; when the 'halt' switch is raised, it would read the PC
> printed when the CPU halted, and display that in LEDs, etc, etc.
> 
> Sounds like an amusing project for someone. Any takers? :-)
> 
>Noel
> 


RE: I want a front panel for my lsi 11 w/switches and lights

2016-03-07 Thread Paul Birkel
Sounds like PDP11GUI ... with the glass-interface supplemented by a
mechanical one?

-Original Message-
From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Noel
Chiappa
Sent: Monday, March 07, 2016 7:41 AM
To: cctalk@classiccmp.org
Cc: j...@mercury.lcs.mit.edu
Subject: Re: I want a front panel for my lsi 11 w/switches and lights

> From: Ed Sharpe

> I want a front panel  for  my lsi 11  w/switches and  lights! 

That's going to be a little tricky. The LSI11 obvously doesn't have a
hardware interface on/in the CPU which would allow a lot of the functions
traditionally found in a front panel (e.g. examining registers, single step,
etc).

Some of them can be done (e.g. a halt/run switch, which LSI-11's already
support), and others could be 'sorta' done - e.g. if the CPU is running, DMA
could be used to read/write memory locations.

Probably the best way to have an emulated front panel is to build a board
that i) emulates the system serial console on the QBUS (i.e. responds to
177560-6), and ii) has a micro or something which uses ODT to emulate the
full range of normal console commands, and drives a set of LEDs and
switches.

E.g. hitting the 'continue' switch when the processor was halted would issue
a 'P' command to ODT; when the 'halt' switch is raised, it would read the PC
printed when the CPU halted, and display that in LEDs, etc, etc.

Sounds like an amusing project for someone. Any takers? :-)

Noel



Re: I want a front panel for my lsi 11 w/switches and lights

2016-03-07 Thread Noel Chiappa
> From: Ed Sharpe

> I want a front panel  for  my lsi 11  w/switches and  lights! 

That's going to be a little tricky. The LSI11 obvously doesn't have a hardware
interface on/in the CPU which would allow a lot of the functions traditionally
found in a front panel (e.g. examining registers, single step, etc).

Some of them can be done (e.g. a halt/run switch, which LSI-11's already
support), and others could be 'sorta' done - e.g. if the CPU is running, DMA
could be used to read/write memory locations.

Probably the best way to have an emulated front panel is to build a board
that i) emulates the system serial console on the QBUS (i.e. responds to
177560-6), and ii) has a micro or something which uses ODT to emulate the
full range of normal console commands, and drives a set of LEDs and switches.

E.g. hitting the 'continue' switch when the processor was halted would issue
a 'P' command to ODT; when the 'halt' switch is raised, it would read the PC
printed when the CPU halted, and display that in LEDs, etc, etc.

Sounds like an amusing project for someone. Any takers? :-)

Noel