[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....

The RC11 is the controller; the drive was called RS64. It may be basically a double-capacity derivative of the DF32. RC11 is quite an obscure device, because it was only around very briefly at the start of the PDP11 era. We had one on the physics lab computer at my college; I think they got it in 1972, running DOS. I wanted to run RT BASIC on it so I worked on getting RT11 V2 to run on it, which required writing a device driver and boot driver. Fortunately, Anton Chernoff was working at the college that year. I asked him why he didn't write an RC11 driver when he was creating RT11 V2 at DEC -- his answer "because we couldn't find one". The 32 word blocksize was a bit of a nuisance because of the RT11 requirement that partial-block writes have to be zero-filled to the next 512 byte boundary. On disks like the RK05, the controller handles that, but on the RC11 the driver had to do any filling from the sector boundary to the 512 byte block boundary. The other thing about the RC11 is that it was so small that few people wanted to deal with it. RSTS only ever supported it as a non-file-structured swap disk, not as a file system. It was handled as a weird appendage to the system disk (boot disk) file structure. paul