Well - to answer a series of questions ;-) There were two separate operating systems available for the B1000 series. There was the standard MCP (that was similar in operational characteristics between the B1000 and B2000 series at least) It didn't have a common code base, but things worked in a similar manner from the console (SPO in Burroughs speak.) The other OS was "CMS" and ran on the B800/B1000 series. CMS was from the Liege plant if I recall (Hans - is this right??) and I remember them showing up in Santa Barbara where we were bringing up the B1965 at the time. We had our MCP up with a couple of issues when the guys came in instruction we'd added on the B1965 if I remember, other than that it came right up! So from my understanding you could run the same applications on the B1000 and B800 series. Now - difference between B18XX and B19XX. Mostly cost reduction and reimplementation in TTL. The B19XX may have been faster (a blistering 6Mhz ;-), likely had a larger memory sub-system, and I think they had the same size instruction cache. The B19XX machines had a 4Kbyte instruction cache. The difference between B1955 & B1965. Well you've all seen how BIG the B1955 was. The B1965 with soft console (which I LOVED working on...) is about the size of a group of desk drawers on a standard desk! Maybe 2.5 feet tall, 20 inches wide, and 24 inches deep. (Real guess on that -but it was a VERY small box.) It was every bit as capable as the B19XX chassis. The Disc Controller was reimplemented as 5 cards using an 8086. There were two data com options, the single line and Multi-line controller. The Multi-line controller was the only "DMA" device in the system and was also a 8086 based design. The soft console was an 8080 implementation. All this stuff had to be field testable/repairable so the soft console designer (Dick Mogia) went to considerable effort in having two paths to do everything. If the UART was dead, he had some 8255 parallel port bits that he could bang out the serial code needed by the console to show the problem through independent transistor drivers if the RS422 drivers were dead! It also controlled the the tape drive used by the system to IPL - the UART did double duty here. With the addition of the UART and a uP driving it, we found out just how bad the tape drives REALLY were. Up until then it was done with a state machine! There were really BAD parity error and tape errors that occured. The tape didn't last long! We had the same kind of issues as the B80's floppy! This was all revealed when we had something on there that could categorize the types of errors we were seeing! I had ALOT of fun working on the machine, and learned alot too! Steve Wilson