Re: Re: Extracting files off “unknown” 8 inch disks. Any thoughts…

Glen Slick glen.slick at
Fri May 5 20:23:11 CDT 2017

As far as RX02 formatted 8-inch floppies go, I have some original DEC
RT-11 V05.01 RX02 format distribution floppies which I managed to dump
to disk images a few years ago. I forget exactly how I did it now.

It was either with a real DEC RX02 drive and an M8029 RXV21 controller
in a Q-Bus PDP-11 system, or with an Scientific Micro Systems SMS1000
which has an RX02 compatible disk controller on its main "foundation
module" for a standard TM848-2E floppy drive.

Then I booted 2.11BSD on one of the two PDP-11 systems and simply used
"dd" to dump all of the floppy sectors to image files, then used ftp
to get the image files out to a modern system. Fortunately I didn't
have to deal with any bad sectors. Not sure how that would have
complicated things if I did.

Next to use those floppy image files with SIMH I had to reshuffle the
sector order into new image files copies. The RX02 driver in software
does a 2:1 sector interleave, a 6 sector per track skew, and starts at
track 1 and wraps around to track 0, which had to be undone.

(See the "raxfactr" routine in the 2.11BSC source file src/sys/pdpuba/rx.c)

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