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Rolm 1602A mil spec computer

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    I guess the screws are UNC #4-40 or #6-32. You can try screws from an old PC whether the big or small ones fit. Will see whether I can find something on the options you have in your CPU - til than good luck in getting hands on some IO/load module to fit your empty slot. Without panel connected the CPU will start at a certain address - probably the 2023 will be located there.


      Just checked and scanned some documentation; following are the pinout of the Control Panel Connector - a straight 1:1 cable connects the panel there. After that there are 7 sheets giving the complete interconnections in case of a 1602B and that may help in wire a (simulated?) panel directly to your CPI board and it may be wise to check the interconnections between CPU and your CPI - just to see whether they match. If so, there is a good chance, that the panel-pins will also be as listed. Good luck:
      Attached Files
      Last edited by baigar; August 23, 2021, 11:38 PM. Reason: Attachments do not seem to show up -> Added the scans directly.


        Jos, by the way: The option 3 of your CPU means "Extreme Temperature Range", which is -55C...95C (rare option I think) and option 15 is pretty common: Microcode includes floating point and BITE (Built In Test) which tests CPU and also some basic memory. As you suspect, the missing memory may be the reason for your "BITE" LED not getting illuminated after power on.


          Thanks for the pinouts. Would have saved me a couple of hours...
          Anyway the 1602A motherboard has the same slots A1-A10, an A11 which is a second MEMOPT slot. It is missing slots E27--E31.

          I will wire some extra signals to the MEMOPT slots ( read(n) and write) .Then a RAM card can be made that would fit both the MEMOPT slots and the external DB37 connectors.

          Appended is a list of the memory DSUB pinouts.
          Attached Files


            So the ebay plugs arrrived and : bad luck. They are M81511/56FE01P2, and should have been M81511/56FE01P1.
            The last 2 stands for "alternate keyring"...

            Should have paid more attention to this : milc81511.pdf

            Anyone know how to open up the plug, i.e. remove the bajonet-ring so i can "adapt" the keyring ?


              Hi Jos, sad that the connectors have the wrong key-ing. I also had to pay some extra money in the past until I learned there is a different keying. In my variant of these plugs (made by Glenair, Series G3703), the bajonett-ring (marked in blue below) is forced backwards using a spring. In this way twisting the bajonett onto the machine's plug applies a constant pressure forcing the pins in. There is a snapring (violett arrow) preventing the ring from sliding of the body towards the cable. Removing this ring allows taking off the bajonett ring towards the cable.


              There are two different ways of keying in these mil-spec plugs:

              (1) The outer noses shown below and marked in the picture below are the same, but the insert is rotated with respect to them. In these there is no easy way of fixing the problem - only approach I successfully followed is given in my blog at datecode 9/11/2017: If you have two plugs, you can drill out the insert in one of them, destroying it. In the other one you cur open the outer body to safely extract the needed insert. From the two intact parts make a new plug.

              (2) The outer noses are at a different position, but the insert is not rotated. In this case it often is convenient using a rasp to remove the noses which are in the way - the main key (marked in blue below) normally can be kept as it is always at the same position.

              Last edited by baigar; August 30, 2021, 07:36 AM. Reason: Typos, formtting and resizing the pictures.


                By accident I came accross an auction on eBay where a Hawk/32 system is listed. That is the latest one of the Rolm series of mil-spec computers, see


                The seller is asking a rediculous price of 99kUSD - OK, that machine is a 32 bit one largely compatible to DG's advanced EAGLE product which sold new obviously for over half a million USD. But I doubt anyone is going to pay that price. This kind of machine was widely used in the Boeing AWACS aircraft or the ATTAS research aircraft. All of these are out of service now and I have been told that the Hawk is a hard to fix machine as it contains lot of ASICs. As all machines before it, it still accepted the 1970's style IO boards - in my opinion a reason for the success of the Rolm machines.

                Maybe a good place to talk more on price In 1971 the 1601 was advertised with a price of USD10550 (today around 71k) - that was the bare machine, arithmetic was +3500USD, panel +750USD and each 8k of memory around +8kUSD. So quite a lot of money these days but a small amount compared to the other computers which where custom for each application in the 1970ties and easily reached 500kUSD.

                In 2000 the repair prices for the 1602A of Jos was around 5kUSD with a refurbished one going for 15kUSD - these numbers amount to 8kUSD and 24kUSD today's value respectively.

                So probably the setup I am running SpaceWar! on was new around 40kUSD in 1974 (220kUSD today's value: 1602 with AD converters, 24k, panel, IO extender etc.) - seen here with homebrew hard drive simulator and attached joystick. Display is a Russian S1-122 oscilloscope:


                Last edited by baigar; September 7, 2021, 05:31 AM. Reason: Minor typos and added the "USD" with the numbers where appropriate ;-)


                  Asking the right persons sometimes yields unexpected results :


                  Certainly not free, but finding these spare parts inside Switzerland was unexpected. That Rolm was an awesome burden on the Swiss taxpayer at the time....

                  Now the question remains whether I need the Rolm 1642 control panel interface, or whether the much less complex Rolm 375 control panel interface I have is suffisant.
                  Attached Files


                    Hey there - pretty cool find! Well done! Even the hard to obtain key is included as well as some cabling! Good luck in firing up your Rolm Doesn't the binder contain some documentation like schematics and/or pinouts you ca use to verify the connections and see whether your "reduced" CPI connects to the right pins? In the end I could probably borrow you a "full" CPI but it seems there are no connections wired from your chassis slot to one of the fron connectors, so (1) it will not be of much help and (2) even it might not fit into your chassis elctrically.
                    Last edited by baigar; December 5, 2021, 02:56 AM.


                      Hi Jos, just one question: The post from 15th of August 2021 shows the chassis from the bottom. The short plugs are the IO-boards and there are two longer ones on the right hand side. Are these the ones supposed to take the memory or is one for CPU and the other for memory (Just trying to figure out what memory PCBs would be needed)?


                        The right-handside DB37 plugs, with the blue wiring, are for an external core-memory box. They match the box connections on your pictures. I have neither the extension box nor the corememory sets, but the internal memory slot, now filled with a PROM board, has ( nearly..) all the signals needed : I am designing a plug-in SRAM board.

                        That front-panel I found is the right one for a 1602A, but unfortunatly I do need an 1642 front panel interface ( anyone has a spare ?...), and I will also need to wire up a connector. Which is just as well as the 1602A and 1602B use different connectors, and the cable that came with the box is for an 1602B...

                        Ah well, keeps you busy....


                          Memory: OK, so your 1602A ONLY has got the D-Sub plugs for supplying an external memory brick and there is no internal free slot for e.g. a CMOS memory module. I just pulled one of the 8k CMOS modules from my 1624 IO processor, which also uses a 5605 CPU and this obviously is not going to fit your machine (no free slot):


                          CPI-Board: Why do you think, that you CPI board is not suitable for driving a panel? The fully populated CPI has got more chips on it to handle TTY and papaer tape than your's - so maybe your's is only a panel interface?

                          In all Rolms I saw, the panel was a single Deutsch plug with 55 pins - the TTY interface was wired to a different plug on the front panel if used (only a few wires to that one and in 1602B onwards it was a 55pin AMP plug instead of a Deutsch as seen in the 1602(A)). The paper tape interface - if used - was again wired to a different plug, so no Y-cables in that case. The wiring in all my Rolms is done directly from the front plug to the plug of the board within the chassis and you mentioned, that there are no wires connected to your CPI board -> Obviously your Rolm is not prepared for connecting a panel, i.e. it starts right after power up to execute code from the ROM.

                          My proposal would be, looking at my post from 8/24 which contains the wiring diagram of a 1602B with CPI board - verify that the proposed outputs of that 1642 CPI board are outputs/inputs in your CPI board. If they are open, you probably need a different CPI board, but if they are connected to some chips, you are with high probability just missing the connection of the appropriate pins to a Deutsch 55 pin connector (pinout also given in my post from last summer).

                          I have got a CPI board pulled from my IO processor, if you did these tests and still are sure that your CPI is not prepared for a panel, than er can probably make some arrangement for a temporary loan of that one or preferred some meeting as I am little reluctand shipping it...

                          Last edited by baigar; December 8, 2021, 12:43 AM. Reason: Typos fixed.


                            I was unclear : my 1602A has 2 memory slots, one of which is occupied by the ROM board, so one slot remains free. Anyhow with more modern RAMs there is enough space left on the board I am designing to add ROM and USB interface. You 8K board is made up with 32 2114 SRAM's 1Kx4, I will used 62256 and 2764. Finding those green connectors will be the main problem.

                            The need for a 1642 CPI : that is what the 1602B manual says. But yes, seeing that I have both a TTY and an RTC board in my 1602A means that it never had an 1642 CPI in the first place. It remains strange that I should have a S375 panel interface board, but no internal wiring for it. Then again I know nothing about the history of my particular machine. As you say : it must have been set up to run from core, or boot from tape, seeing as this is the only mass storage controller inside.

                            My 1635 frontpanel has a 55 pin Bendix socket with matching cable, not compatible with the Deutsch 55 pin socket. So changing some sockets on my machine is a must.

                            So tasks in order are :
                            1) finish the RAM board, check "bite" function.
                            2) as you suggested : draw up schematic of my S375 CPI board and check if it can drive a 1635 panel.
                            3) find out existing wiring between sockets & IO boards. Find out which socket is going to be redirected to front-panel duty, wire up the front panel using a Bendix socket. ( or create a cable with a Bendix plug on one end, and a Deutsch on the other.
                            4) find either a 1642 ( and rewire again.. ) or find a 3320 papertape reader if board, as I would like to have papertape functionality for this machine.

                            Journey is only starting !


                              Thanks for the explanations to Jos. So:

                              Ad 1: I will put my 8k core boards back into the 1626 IO processor.
                              Ad 2: Probably no full schematic is needed; I'd just look at the pins relevant to controling a panel (see wirings scheme posted 8/24)
                              Ad3: What I can offer would be a new breakout cable just found in my spares box at the very bottom - you could wire that to the mainboard as it is done with the Deutsch plugs and the IO connections right now. You could unscrew one of the original Deutsch receptables and push it back into the chassis and the new Bendix receptable would replace it:

                              That will work if one of your cables fits the panel and the other and matches the receptable shown above. Let me know and I am sure we can make some deal and I will send out the insertion/removal tool together with the breakout cable.

                              Ad4: Maybe at some time in the future a paper tape board will show up somewhere. Often one gets lucky unexpected


                                That is most certainly the correct plug for the panel / panel cable i have ! Would be a good way to proceed...