Hi, some people from the "Rechenwerk Halle" (http://9hal.ath.cx/usr/digital-ag/projekte/andere/museum/) ..a bunch of people that is interested in historical computing got an Robotron K1840 DEC 11/780 clone lately and they try to get it running again. (freinds of mine). Unfortunately a thing called SKR Busadapter (Massbuss adapter) and the entire console computer are missing. So far as I know is the main CPU 100% compatible to the DEC original using an UNIBUS System, PCBs are exchangeable, but the Console Computer is not. In The K1840 this is a K1620 Computer, the CPU is build from 8 Bit NMOS slices (U830) and ordinary EPROMs (https://de.wikipedia.org/wiki/U830C) using a mechanical different PCB System. The same system was used in the K1630 PDP11-alike (see below) which had an MMU (K1620 has none). The Main difference that's preventing unpatched OSes are the U834 Bus interface ICs, that must be software configured before the devices can be accessed from the QBUS-like System Bus. The U834 are containing the Bus drivers and all needed registers for interrupt and DMA and the entire address decoder logic needed for QBUS Systems which simplified the interfaces somewhat. Nevertheless of that progressive design, it was the worlds slowest PDP11.. In the K1840 ordinary TEAC FD55FV Floppies (2x) where used for the console System to boot up the system. So far so good (or bad). There are a few things that I want to know now.. I know that in the original 11/780 the Console CPU was an 11/03 with some interface to load the VAX Microcode in to the main CPU. Do you think it is possible to use an ordinary 11/23 instead? What Floppy Controller was used in the original, I know that there was a single 8" floppy drive in the 11/780 and don't think that the controller was the usual RX01 or RX02 System...? That's an article from the german magazine C't about the people which got the K1840: http://www.heise.de/newsticker/meldung/Rechnende-Schrankwand-Computermuseum… That's the K1840 on the left: http://9hal.ath.cx/usr/digital-ag/log/K1840_im_Rechenwerk.jpg and The K1630 .. PDP11 not so "clone" on the right. I don't think that the Tape drive was shipped with that machine, the bulgarian original looked different so far as I remember.. Is there someone that would help out them with missing hardware/software? Regards, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583 www.tsht.de, info at tsht.de, Fax +49 3731 74200, Mobil: 0172 8790 741