Extracting files off unknown 8 inch disks. Any thoughts

allison allisonportable at gmail.com
Fri May 5 10:10:45 CDT 2017

On 05/04/2017 09:27 PM, Fred Cisin wrote:
> Thank you!
> Now, the question will be whether Allison has some free time to check
> them out for Terry.
I could...  If I had the time and no other competing projects.

I'm far from the only one around with a PDP-11 with RX02 or a
microVAX-II with a
RXV21/RX02 spare to swap in.

The process would be reading the media and transfering to a PC via
serial line at
maybe 19.2K.

If the media is good its not so bad at 500k max.  If the media is past
its "use by"
date it will gum the heads and require pulling out the drives to clean
the heads.
Thats time consuming.  If the format is not as expected then it s a read
capture sectors project, more time. 

The key is are you sure the media is formatted as ODS-II?   I'd consider
that very
unlikely as the overhead is high.  Even VAXen could save to small media
multiple formats not the same as whats on the big RDxx, RLxx, RAxxx or
RZxx media.
Typical it is likely files-11.

Suggesting to Terry, learn DEC systems.

One or two for giggles maybe, a significant volume of them comes with
cash as
its a time consuming commercial effort.


> 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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