hi there! well the pdp was once a pdp 11/23+ so enclosure and backplane should be the same as a 11/23 (ba 23). backplane should be Q22/CD configuration, but i´ll open the box and look for the 501- number to be sure. on the back there is a sticker saying this is a 11/73. the cpu-board is a 11/83.(i´ll pass the number too). do all 11/83 use PMI ? but the memory seems to work, or has the cpu board some memory on it? when i picked up the box they booted it, i suppose this configuration was the way they used it there and should have worked. the RD54 controller has a 50pin ribboncable wich goes to a small board (wich was hanging on the backside) and a small frontpanel (from a 11/83 or 73) was hanging on it. it looks like ************* * *'''''* O is a round hole (to hold a batch?) * O *'''''* '' is a big hole (power switch i suppose) * *'''''* ************* * X B * X = run on/off ?(green led) B = reset ? * X X * X = write protect(red led) X = online(green led) for disk 0 ? * X X * X = write protect(red led) X = online(green led) for disk 1 ? ************* X is a switch with led B is a button with led i never saw a pdp with this frontpanel, and since there is nothing written on it, i tried to compare with a picture found on the web, but i´m not sure if i´m right. can someone tell me if i´m right ? i asked those guys from where i picked up the box, but they told me that the last guy using the pdp left some years ago, and in 1999 they just powered it off. this explains also the small paper sticking on the pdp that showed how to login and shutdown the box. root password is written on it *g*. tomorrow i´ll open the box again. thanks for your fast response. -- lothar FWIW, I don't know about the tape error, but that layout looks OK apart memory shold be in the first slot and the CPU in the second. The essential difference between an 11/73 and an 11/83 is that the 11/83 uses PMI memory. Assuming your backplane is the right one, in a BA23 or BA123 box, and that your memory is a single 4MB board, you should swap them round, otherwise what you actually have is an 11/73. I assume your RD54 controller is a genuine DEC RQDX3, so it's in the right place. It's possible you have an old version of the firmware on it, but it should still work even if you do. all the planes in the backplane are genuine dec parts. -- Pete What enclosure? BA23? If yes you have empty slots between the cards as this box has 3 Q/CD slots on top and 5 Q/Q slots below. Have a look at the QBus HOWTO at http://vaxarchive.sevensages.org/ -- tschuess, Jochen