Hi, I recently aquired an old Netcom system and I'd like to find out a bit more info about this backplane. It's an 11/23 system (based on CPU) . It has some standard DEC cards in it (M8186 CPU, DLV11, BDV11 bootstrap board ) as well as a thrid party 256Kb memory board and an MXV22 floppy controller. Apparently the system ran RT-11 from floppies a few years back before it was put in storage. I have read through the PUPS archives, esp. a post from Michael Sokolov back in 98, where he describes the different types of QBus'es. Q/Q, Q/CD etc. Have also read through the info on hampage.hu and various other sites that host PDP11 related info, but am still unsure about this particular beast. It looks like the backplane that I have (according to the archives and some documents written at SLAC in late 70's) is a serpentine or sinusoidal type configuration. The SLAC documents actually refer to the Netcom backplane but they describe it a simple serpentine type. A diagram on my cardcage describes it as follows: A B C D ------------> <----------- -------------> <------------ There is also a blurb about slot 2/CD being wired differently. Two slots on the diagram are pre-printed for RL controllers. I can't rembeber the exact wording, since I don't have the computer in front of me. It gather that I insert the CPU in 1AB, then rather than putting the next card in 2AB, I would place it in 1CD. Next would be 2CD and so on ,snaking down the line. Is this correct? While this is all fine for dual cards, but how does this configuration handle quad cards? I'm guessing that it has to do something with that 'blurb', but that would mean that I can only have one quad card installed, and it would be right towards the begining of the bus. The BDV11 should be the last card in the chain from what I can remember. Also, my CPU card is a rev. D so it can do 22bit addressing. I'd like (if possible) to run 22bits, since this would allow me at a later time to put in a 11/73 cpu that would give me more flexibility in what OS's i can install on the machine. I'll have to check if the backplane is wired for 22bits or not. I seem to remeber the standard qbuses had the W1-W4 pins (?) that you could wirewrap to change from 18to22 (i'm assuming that this operation propagated the BDAL17-20 from slot 1 to the other slots) but this backplane has nothing like that. I'm planning on checking it with an ohmmeter, and it should be very obvious if these signals are present across slots. The backplane is a PCB style, but it does have std. wire wrap pins sticking out from the PCB. If the BDAL17-20's are not present across slots, can I just simply extend them thru by wirewrapping? If anyone can shed any light on this backplane, it would be greatly appreciated. thanks in advance for any replies. -- alex