"New" PDP-8

Well, other than a few extremely minor hardware changes, I did -absolutely- no design work on this, Mr Armstrong did over the course of many years! How it worked was this: 1. He has a PDP8 emulator for Windows, which does emulate an RK05, and also the RAM chips in the "real" design. 2. He wrote device drivers for the RAM and the IDE drive in assembler, which you assemble with PAL8 and put on an emulated RX01 so that the RAM disk can be mounted. 3. Then, you SYS one of the RAM disks with the RAM disk bootable. 4. Then, you download that RAM image to the BTS6120 (single board PD8) and boot from that. 4. Then, you sys the IDE drive in the physical BTS6120 design so that it is bootable. 5. Then, you copy stuff from the RAM disk in the emulator to the RAM disk in the BTS6120, and repeat. So, the RAM and IDE drives are "legitimate" OS8 devices. The IDE is broken up into 8 partitions of about 2 MW each (so even the oldest IDE drive that supports LBA, which any drive over 600 meg probably does) will work. I used the 2.5" drive only for space and power reasons. An additional complication was that the 512Kx8 ram chips in the original design (static, low power) were quite expensive for four of them so I used 128K ram chips that I got on a good deal instead. So I had to cut 3/4 of the disk image off(after "squishing" - packing the disk of course) before downloading. So I had to repeat (5) above several times. It took me almost as long to figure out how to do this as it did to build it. Mr. Armstrong was as helpful as he could be but there was no substitute for "pounding it into submission". On the 6120 chips (I don't think you could use 6100 chips in this) - I got mine socketed in a DECmate CPU board for $25.00. I'm getting a few as a spare. A drag about the DECmate board was that its a multilayer board, and in spite of my best desoldering efforts, the chips are trimmed short and you can't really use many parts from it other than the socketed BTS6120 and a few EPROMS. Bob Armstrong has PCB's available but they are pretty expensive because they are multilayer and lets face it, he can't have hundreds made at a time. On the other hand, I paid myself about $5.00 an hour wire wrapping instead! --- Heinz Wolter <h.wolter(a)sympatico.ca> wrote: __________________________________________________ Do You Yahoo!? Yahoo! Greetings - send holiday greetings for Easter, Passover http://greetings.yahoo.com/