> On Apr 15, 2024, at 10:05 AM, Christopher Zach via cctalk
> <cctalk@classiccmp.org> wrote:
>
>> If you want word-addressable, the RF11 will do that. Not the RC11, it has
>> 32 word sectors.
>
> Oh yeah, the pdp11 world had a DF32 like thing with the RF11. Totally forgot
> about that one.
>
> C
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
