pdp11 CPU on S100 board? Given that old Soviet knockoffs of pdp11 cpus can be found on ebay, I was wondering if anyone else has thought of making S100 boards containing said processors. -- David Griffith dgriffi at cs.csubak.edu <http://www.classiccmp.org/mailman/listinfo/cctalk> A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? -----reply----- Hi Dave, In theory, I don't see anything preventing an S-100 PDP11 CPU board. The only practical concern is there would not be enough demand for the boards to make even small batches of manufactured PCBs economical. This has proven to be the limiting factor the hobbyist projects I've seen. At N8VEM and S100computers.com, we already have about 15 or so boards including an S-100 Z80 CPU board, with a second prototype board of an S-100 68K CPU board on the way, a third prototype board of an S-100 8086 CPU board imminent, and a first prototype board for an S-100 6502 CPU board soon. So certainly there are many CPUs which can be implemented on S-100 boards as bus masters. However, these are all fairly popular mainstream CPUs and are likely to have enough hobbyist interest to warrant at least a small run of manufactured PCBs. I doubt anyone knows for certain how much demand there would be for an exotic S-100 PDP11 CPU board however I'd be willing to support a community project along the lines of the vintage-computers.com XT-IDE, AT2XTKBD, SCSI to IDE/CF, and FM Synth efforts. My role is mostly the schematic capture, PCB layout, and getting the prototype boards made. I am assuming you or someone else would have the knowledge to make the schematic and perform the initial build and test debugging. I don't know much about PDP11 since it is outside my interest area. Using the S-100 bus has some advantages in that we already have a fairly complete suite of peripheral boards already such as RAM, ROM, floppy disk, hard disk, video, serial IO, RTC/PIC, etc. The project could focus solely on making the S-100 PDP11 CPU board a bus master much like the S-100 68K CPU board already in development and just reuse the rest of the boards "as is". This has made initial build and test of our S-100 8086 CPU board *dramatically* easier. By using the S-100 EPROM board, S-100 4MB SRAM board, S-100 Serial IO board, etc the S-100 8086 CPU board booted CP/M-86 almost right away. Very nice! A community project would start with a schematic and PCB layout which should be fairly straight forward to do. Next would be getting some prototype boards which would be typically $30 each if we went the www.33each.com route $150 for 5 PCBs. If a lot of builders wanted to participate we could get a batch of 10 from PCBcart.com for probably around $250 for 10 PCBs. However, as you probably know already the track record for community projects, especially at CCTALK, is pretty poor. Probably the best bet would be to take it elsewhere to improve the "signal to noise" ratio. I am aware of another S-100 hobbyist project that is working to make a multiple board custom 32 bit RISC CPU system. It is quite impressive in scope but well beyond my skill set. Thanks and have a nice day! Andrew Lynch