On Jul 11, 12:02, Jochen Kunz wrote: (You mean BC1 and BD1, not BD2) No, but it's nothing that's used in any normal system. They don't connect to the M8014, nor to anything a standard 18-bit system can access (they're SSPARE4 and SSPARE5 bus lines, normally unused, although the 11/03 and soe contemporary options did put odd signals there). My guess is they're for some manufacturing test, because a quick perusal of the RLV11 Technical Manual didn't tell me anthing either. The M8013 I just pulled from one of my (22-bit PDP-11) systems has those two tracks cut, and it's been working fine since I've had it (almost 15 years). If you hold the M8013 component side up, with the contact fingers towards you, they're the two thin tracks in the shape of an inverted "L" which come from the 15th and 16th contacts on the third set. They're cut about halfway between the contact finger and the corner of the inverted "L". I've had a look, but I can't find the ECO relating to this. Either my microfiche is too old (quite likely -- it only lists up to CS Rev F and my RLV11 is Rev H) or I saw it somewhere like in one of the Micronotes (which I no longer have, and sadly the ones available online are only a fraction of the total issued). DMA Go for it... -- Pete Peter Turnbull Network Manager University of York