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matu
December 16th, 2009, 06:30 AM
I have some 8 inch floppy disks from an old S/36 that I got on e-bay. I was going to write PDP-11 boot images to them but before I do that I'm wondering if I can dump their contents. I can read all 32 sectors on track 0 using an RX02 drive but no other tracks.
Typical contents look like


Sector 000002
003476 / 040345 040100 040100 040100 040100 040100 040100 040100 / .@@@@@@@@@@@@@@@
003516 / 040100 040100 040100 040100 040100 040100 040100 040100 / @@@@@@@@@@@@@@@@
003536 / 040100 040100 040100 040100 040100 040100 040100 040100 / @@@@@@@@@@@@@@@@
003556 / 040100 040100 040100 040100 040100 040100 040100 040100 / @@@@@@@@@@@@@@@@
Sector 000003
003476 / 053400 153334 000000 000000 000000 000000 000000 000000 / .W..............
003516 / 000000 000000 000000 000000 000000 000000 000000 000000 / ................
003536 / 000000 000000 000000 000000 000000 000000 000000 000000 / ................
003556 / 000000 000000 000000 000000 000000 000000 000000 000000 / ................
...
Sector 000006
003476 / 161742 161701 141311 161324 161350 142743 171724 040366 / ...............@
003516 / 000100 000001 000000 000000 000000 000000 000000 040100 / @.............@@
003536 / 040100 040100 040100 040100 040100 040100 040100 040100 / @@@@@@@@@@@@@@@@
003556 / 040100 040100 040100 040100 040100 040100 040100 040100 / @@@@@@@@@@@@@@@@
Sector 000007
003476 / 153345 170723 141311 144724 142331 040100 040100 040100 / ..........@@@@@@
003516 / 040100 040100 040100 040100 141311 161324 161350 142743 / @@@@@@@@........
003536 / 171724 040366 153100 152746 154705 142311 040100 040100 / ...@@.......@@@@
003556 / 040100 040100 040100 040100 040100 040100 040100 040100 / @@@@@@@@@@@@@@@@
Sector 000010
003476 / 142310 170731 075500 144723 154702 154701 040350 040100 / ....@{.......@@@
003516 / 040100 040100 040100 170760 171360 154764 170760 170360 / @@@@@@..........
003536 / 171761 172367 170361 040370 040100 142500 170303 174362 / .......@@@@.....
003556 / 170771 170762 170360 171361 040370 040100 040100 040100 / .........@@@@@@@
...

...
The data is dumped in octal, the text is ascii, although I would guess EBCDIC might have been a better way. Does anybody know how to interpret this?

Chuck(G)
December 16th, 2009, 02:06 PM
Hex, not octal is definitely the way to look at these. And yes--it's EBCDIC. On a S/36 disk, the first track is FM; the remaining tracks are MFM. Your RX02 can read the FM fine, because it's basically compatible with RX01 format. But RX02 MFM is like no one else's MFM--sector headers are recorded as FM, but sector data is recorded as MFM, with some substitution in some of the data patterns so as not to confuse the FM IDAM and DAM recognition.

A PC will read the remaining sectors on the drive just fine.