Extracting files off unknown 8 inch disks. Any thoughts

Fred Cisin cisin at xenosoft.com
Thu May 4 20:27:27 CDT 2017

Thank you!

Now, the question will be whether Allison has some free time to check them 
out for Terry.

Experience always beats speculation:

On Thu, 4 May 2017, allison wrote:
> First if they are DEC its one of two formats either FM aka RX01 or FM2
> aka RX02.
> RX01 base format is 128byte sectors and 26 per track  PC can read them.
> RX02 base format is 256 bytes per sector byte the timing encoding is
> totally
> unreadable with any LSI controller.  It uses FM headers to confuse the act.
> To read that you need:
> - RX02 and a compatible system.
> -  one of the many DEC clones (DSD, and many others usually using 8X300
> family chips)  in a DEC box (and cpu).
> -Catswesel or one of the other flux readers in a PC.
> Note the RX02 drive is dual format, it can read/write rx01 media ( 8"
> SSSD).  It can also read and write
> RX02 format or "init" RX01 media to RX02 format and back to RX01.   RX02
> format was unique to DEC
> and the only other that could read or write it were DEC hardware
> compatible controllers.
> First you have to satisfy the first (able to read sectors) to do the second.
> Then the possible 8" ODS formats are....
> DEC format (RX01 or 2) include PDP-8 family mostly OS8 (odd 12bit
> formatting).
> The  PDP-11 group  RSX, RSTS, RT11, unix, are most common.  Note PDT150
> is also PDP-11 RX01.
> This was the most likely and populous hardware group using RX01/2 disks.
> The Qbus PDP-11 systems could also support RQDX controller for 5.25 and
> 3.5 inch floppies. That made later systems with RX01/02 less common over
> time.
> VAX, 11/78x uses a PDP11 (LSI11) to load microcode.  It is PDP11 and
> RX01 media.
> Most of the later systems *if* they have 8" RX drives are likely any
> format compatible with
> the PDP-11 group as that's the likely exchange partner/target.
> I've not seen VAX format on RX01/2 media, its not impossible except for
> the VAX78x family
> as the PDP11(lsi-11) physically own the drive.   To do that it had to
> have a unibus  RX controller
> and a RX01/2 drive and then the file format can be anything as VMS had
> utilities for most all the
> PDP11 formats.
> Latter vaxen used RL02 or TU58 or other media to load microcode.
> Microvax and later machine
> did not load microcode save for exception code during the normal boot
> sequence.   In those
> cases a RX01/2 was unusual to the extreme save for maybe a Qbus microvax
> (not a supported config)
> assembled as a hack.  Most of the Qbus VAX systems with floppy used
> RX33(5.25" RX50) or RX23(3.5")
> as the RQDX1/2 controllers supported 5.25" floppies initially and later
> firmware supported 5.25" Teac
> and 3.5" Sony drives as well.  RQDX3 5.25" Teac and RX50  and 3.5" Sony
> drives.  Because of this
> and far more space per drive RX01/2 was rarely used.  The RQDX
> controllers could do the stated
> floppies even is MFM  disks were not connected.
> Also the VAXes may have run unix and that was likely user save media.
> in short if RX01 anything that can read SSSD 8" is good enough.  IF RX02
> a pdp11 and RX02(or third party
> equivalent) makes it easy.    To do RX02 on PC you must have a flux
> reader, 765 and later clones cannot.
> How do I know.  I have PDP-8, PDP11 (with RX02) and VAX (qbus uVAX,
> uVAX2000, and 3100 family).
> I used to and still do exchange between RT-11 and CP/M using RX01 mode
> and a CP/M utility that
> knew RT11 format.  IF it was RX02 media, I'd rewrite on the PDP11 to
> RX01 media using FIT or other
> tools.
> Allison

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