On Sep 14, 2012, at 9:56 AM, Paul Anderson wrote: You can usually build an 11/23+ out of easily-available parts on eBay for less. To play around with, all you really need is a CPU board (ideally with a serial port built in, else you will also need an SLU), some RAM and a backplane. My base system is a KDF11-BA (11/23+ CPU board with serial and boot ROM) and a 256K RAM module, which is enough to start playing around with things. If you only have a backplane, MAKE SURE you put a reasonably powerful fan blowing through so that you don't overheat things. Buying off eBay, of course, is the expensive way; if you're lucky, you may strike a deal with folks here or elsewhere. Or if you live in the right kind of area, you may find discarded systems in the skip or on Craigslist (Philadelphia is not a target-rich environment, sadly). For media, you can use one of the many available TU58 tape emulators; the TU58 attaches via serial, so you can use a modern PC as the host for that and have your media without getting extra peripheral boards. Once you graduate from that (since it is quite slow), many other Qbus media options are available, including SCSI cards (or my generic Qbus card, if I ever have the free time and money to build it). - Dave

If you are anything like the other hardware addicts on this list, then a Unibus model might be the only thing that will offer sufficient satisfaction. What software do you want to run? How many hours a day or a year will you run the system? Do you have any experience running a PDP-11? Would an emulator (Ersatz-11 or SimH) be helpful until you understand what you want to actually do? You may be able to find a Qbus model that someone is discarding. A PDP-11/73 in a BA23 box would be about the most efficient. A hard disk is not essential, but is strongly recommended. What city are you located in? In the US, there will be more hardware available than in other countries. Jerome Fine

'PDP' = 'Programmed Data Processor' and covers at least a dozen families of machines, with wildly different characteristics. The most common families are ,I think the PDP8 and the PDP11. The former is a 12 bit machine, the latter a 16 bit one. AS fro what to dlook for, theis depends -- a lot -- on why you want it. All I can say is what _I_ would look for, for what _I_ want. Since I am very much a hardware person, I would look for an older machine with the PCU built form mall-ish ICs (TTL, bipolar PROMs), For a PDP11, that means a Unibus machine, and not all of thsoe are suitable. My advice is to think what's important to you (things like blinkenlight panel, TTL-built CPU, ability to run a particualr OS, what sort of pewripherals do you want (do you want demountable hard drives or winchesters, for exemple). They you can decide on aome suitable machiens. and then you can work out how to pay for them ;-) -tony