Re: [Simh] 8" Floppy disk image getting HALT error

[Johnny Billquist]

Walker, the commands Tim show are for if you are running VMS. You can 
run VMS under simh, using the VAX simulation.
Then you could connect the images to that running instance, and access 
the floppies using those commands.


However, I strongly suspect that wont be much of a help. From what 
you've described so far, it does not sound like there is any "normal" 
file system on the floppies, but just the text document straight out.
As such, no OS will help you much. You can just read the document out 
from the dump you have. If you have an OS, it can read the disk giving 
you the disk blocks again, but in the end it will be the same blocks you 
already have in the original dump. No further interpretation will 
happen, so it would just be an extra step in order to get the disk 
blocks inside the OS you might be running. But then you probably want to 
get those disk blocks out again, so than you're back to what you already 
have.


I would just grab the disk image you have, open it in some sensible 
editor, and just cut the parts out that is not a part of the document, 
and that's about it.


But then again, this is all based on how I have understood what you have 
described, and there might be bits I'm missing.


Johnny

On 2017-07-25 18:19, Walker Sampson wrote:

Hi everyone,



Thanks again for the help, this has been great. I’ve had a chance to
loop back to this.



Tim, I’m not familiar with the VMS commands you’re referring to. Is this
a virtual machine I can run – something like OpenVMS? I’m unclear on how
to best access the content on the disk image as a file, given that it’s
not a bootable disk the SIMH VMs can run.



Best,



Walker





*From: *Simh <simh-boun...@trailing-edge.com> on behalf of Kevin Handy
<khandy2...@gmail.com>
*Date: *Friday, July 14, 2017 at 3:21 PM
*To: *Johnny Billquist <b...@softjar.se>
*Cc: *"simh@trailing-edge.com" <simh@trailing-edge.com>
*Subject: *Re: [Simh] 8" Floppy disk image getting HALT error



Just did a little research on WPS-8 floppy format, just to satisfy my
curiosity.

WPS-8 stores data on an RX-50 as a series of 12-bit words, using two
bytes on the floppy to store a word. The low 8 bits goes into the 1st
byte, and the upper 4 go into the second btype.  4 bits in the secnd
byte are unused.

It stores two 6-bit characters in each word. To convert it to asCII,
mask off the 6 bits and add 31. Character 63 (ASCII 94) is a command
character, and following character(s) specify the command. Some other
characters are also special '[' and ']'  toggle upper/lower case.

Looking at a WPS-8 floppy in raw mode on a PC would not display anything
readable, so this guys floppy is obviously not wps-8,and if all pdp-8s
systems handled floppies the same way (as 12 bit words), it probabl
isn't from any psp-8.





On Wed, Jul 12, 2017 at 4:33 AM, Johnny Billquist <b...@softjar.se
<mailto:b...@softjar.se>> wrote:

On 2017-07-12 02:04, Timothe Litt wrote:

On 11-Jul-17 18:02, Johnny Billquist wrote:

On 2017-07-11 21:09, Timothe Litt wrote:

VMS mount /over=id /foreign is the quickest way to
identify files-11 and
RT disks.  FILES-11 can be read directly; use EXCHANGE
for RT-11.  Once
you have the disk mounted on VMS, you can network it to
wherever you
like.


Similar story if you have RSX. I might have forgotten a
thing or two
about VMS here, but I would have thought /OVER=ID/FOREIGN
would not
then let you access the disk in the direct way if it is
Files-11.

I was suggesting the easiest way to IDENTIFY the media.
/FOREIGN will
dump the filesystem type when it looks for a HOM block.  Once
you know
that, you use the appropriate command / utility to access that type.

To access FILES-11 on VMS, you don't use /FOREIGN, just mount
(though
/over=id will allow a private mount without knowing the volume
label.)


Ok. Fair enough. I thought you meant that you'd mount it that way,
and then go at it.

MOUNT and EXCHANGE details are available from HELP and the manuals.

VMS has, arguably, the most filesystem support and tools for
this.  But
OS choice is a religion.  Use whatever you believe in & have
available;
there is no point in arguing religion.


True. And, as with any religion, there is no point of even having an
argument. Whatever works is good enough.

Of course, if the OP is more interested in the result than the
process,
he can probably get one of us to extract the one file for him...


Also true. I'm sure plenty of people would help, if asked.



Johnny

--
Johnny Billquist  || "I'm on a bus
  

Re: [Simh] 8" Floppy disk image getting HALT error

[Walker Sampson]

Hi everyone,

Thanks again for the help, this has been great. I’ve had a chance to loop back 
to this.

Tim, I’m not familiar with the VMS commands you’re referring to. Is this a 
virtual machine I can run – something like OpenVMS? I’m unclear on how to best 
access the content on the disk image as a file, given that it’s not a bootable 
disk the SIMH VMs can run.

Best,

Walker


From: Simh <simh-boun...@trailing-edge.com> on behalf of Kevin Handy 
<khandy2...@gmail.com>
Date: Friday, July 14, 2017 at 3:21 PM
To: Johnny Billquist <b...@softjar.se>
Cc: "simh@trailing-edge.com" <simh@trailing-edge.com>
Subject: Re: [Simh] 8" Floppy disk image getting HALT error

Just did a little research on WPS-8 floppy format, just to satisfy my curiosity.
WPS-8 stores data on an RX-50 as a series of 12-bit words, using two bytes on 
the floppy to store a word. The low 8 bits goes into the 1st byte, and the 
upper 4 go into the second btype.  4 bits in the secnd byte are unused.
It stores two 6-bit characters in each word. To convert it to asCII, mask off 
the 6 bits and add 31. Character 63 (ASCII 94) is a command character, and 
following character(s) specify the command. Some other characters are also 
special '[' and ']'  toggle upper/lower case.
Looking at a WPS-8 floppy in raw mode on a PC would not display anything 
readable, so this guys floppy is obviously not wps-8,and if all pdp-8s systems 
handled floppies the same way (as 12 bit words), it probabl isn't from any 
psp-8.



On Wed, Jul 12, 2017 at 4:33 AM, Johnny Billquist 
<b...@softjar.se<mailto:b...@softjar.se>> wrote:
On 2017-07-12 02:04, Timothe Litt wrote:
On 11-Jul-17 18:02, Johnny Billquist wrote:
On 2017-07-11 21:09, Timothe Litt wrote:
VMS mount /over=id /foreign is the quickest way to identify files-11 and
RT disks.  FILES-11 can be read directly; use EXCHANGE for RT-11.  Once
you have the disk mounted on VMS, you can network it to wherever you
like.

Similar story if you have RSX. I might have forgotten a thing or two
about VMS here, but I would have thought /OVER=ID/FOREIGN would not
then let you access the disk in the direct way if it is Files-11.
I was suggesting the easiest way to IDENTIFY the media.  /FOREIGN will
dump the filesystem type when it looks for a HOM block.  Once you know
that, you use the appropriate command / utility to access that type.

To access FILES-11 on VMS, you don't use /FOREIGN, just mount (though
/over=id will allow a private mount without knowing the volume label.)

Ok. Fair enough. I thought you meant that you'd mount it that way, and then go 
at it.
MOUNT and EXCHANGE details are available from HELP and the manuals.

VMS has, arguably, the most filesystem support and tools for this.  But
OS choice is a religion.  Use whatever you believe in & have available;
there is no point in arguing religion.

True. And, as with any religion, there is no point of even having an argument. 
Whatever works is good enough.
Of course, if the OP is more interested in the result than the process,
he can probably get one of us to extract the one file for him...

Also true. I'm sure plenty of people would help, if asked.


Johnny

--
Johnny Billquist  || "I'm on a bus
  ||  on a psychedelic trip
email: b...@softjar.se<mailto:b...@softjar.se> ||  Reading murder 
books
pdp is alive! ||  tryin' to stay hip" - B. Idol
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Re: [Simh] 8" Floppy disk image getting HALT error

[Kevin Handy]

Just did a little research on WPS-8 floppy format, just to satisfy my
curiosity.

WPS-8 stores data on an RX-50 as a series of 12-bit words, using two bytes
on the floppy to store a word. The low 8 bits goes into the 1st byte, and
the upper 4 go into the second btype.  4 bits in the secnd byte are unused.

It stores two 6-bit characters in each word. To convert it to asCII, mask
off the 6 bits and add 31. Character 63 (ASCII 94) is a command character,
and following character(s) specify the command. Some other characters are
also special '[' and ']'  toggle upper/lower case.

Looking at a WPS-8 floppy in raw mode on a PC would not display anything
readable, so this guys floppy is obviously not wps-8,and if all pdp-8s
systems handled floppies the same way (as 12 bit words), it probabl isn't
from any psp-8.



On Wed, Jul 12, 2017 at 4:33 AM, Johnny Billquist  wrote:

> On 2017-07-12 02:04, Timothe Litt wrote:
>
>> On 11-Jul-17 18:02, Johnny Billquist wrote:
>>
>>> On 2017-07-11 21:09, Timothe Litt wrote:
>>>
 VMS mount /over=id /foreign is the quickest way to identify files-11 and
 RT disks.  FILES-11 can be read directly; use EXCHANGE for RT-11.  Once
 you have the disk mounted on VMS, you can network it to wherever you
 like.

>>>
>>> Similar story if you have RSX. I might have forgotten a thing or two
>>> about VMS here, but I would have thought /OVER=ID/FOREIGN would not
>>> then let you access the disk in the direct way if it is Files-11.
>>>
>> I was suggesting the easiest way to IDENTIFY the media.  /FOREIGN will
>> dump the filesystem type when it looks for a HOM block.  Once you know
>> that, you use the appropriate command / utility to access that type.
>>
>> To access FILES-11 on VMS, you don't use /FOREIGN, just mount (though
>> /over=id will allow a private mount without knowing the volume label.)
>>
>
> Ok. Fair enough. I thought you meant that you'd mount it that way, and
> then go at it.
>
> MOUNT and EXCHANGE details are available from HELP and the manuals.
>>
>> VMS has, arguably, the most filesystem support and tools for this.  But
>> OS choice is a religion.  Use whatever you believe in & have available;
>> there is no point in arguing religion.
>>
>
> True. And, as with any religion, there is no point of even having an
> argument. Whatever works is good enough.
>
> Of course, if the OP is more interested in the result than the process,
>> he can probably get one of us to extract the one file for him...
>>
>
> Also true. I'm sure plenty of people would help, if asked.
>
>
> Johnny
>
> --
> Johnny Billquist  || "I'm on a bus
>   ||  on a psychedelic trip
> email: b...@softjar.se ||  Reading murder books
> pdp is alive! ||  tryin' to stay hip" - B. Idol
> ___
> Simh mailing list
> Simh@trailing-edge.com
> http://mailman.trailing-edge.com/mailman/listinfo/simh
>
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Re: [Simh] 8" Floppy disk image getting HALT error

[Johnny Billquist]

On 2017-07-12 02:04, Timothe Litt wrote:

On 11-Jul-17 18:02, Johnny Billquist wrote:

On 2017-07-11 21:09, Timothe Litt wrote:

VMS mount /over=id /foreign is the quickest way to identify files-11 and
RT disks.  FILES-11 can be read directly; use EXCHANGE for RT-11.  Once
you have the disk mounted on VMS, you can network it to wherever you
like.


Similar story if you have RSX. I might have forgotten a thing or two
about VMS here, but I would have thought /OVER=ID/FOREIGN would not
then let you access the disk in the direct way if it is Files-11.

I was suggesting the easiest way to IDENTIFY the media.  /FOREIGN will
dump the filesystem type when it looks for a HOM block.  Once you know
that, you use the appropriate command / utility to access that type.

To access FILES-11 on VMS, you don't use /FOREIGN, just mount (though
/over=id will allow a private mount without knowing the volume label.)


Ok. Fair enough. I thought you meant that you'd mount it that way, and 
then go at it.



MOUNT and EXCHANGE details are available from HELP and the manuals.

VMS has, arguably, the most filesystem support and tools for this.  But
OS choice is a religion.  Use whatever you believe in & have available;
there is no point in arguing religion.


True. And, as with any religion, there is no point of even having an 
argument. Whatever works is good enough.



Of course, if the OP is more interested in the result than the process,
he can probably get one of us to extract the one file for him...


Also true. I'm sure plenty of people would help, if asked.

Johnny

--
Johnny Billquist  || "I'm on a bus
  ||  on a psychedelic trip
email: b...@softjar.se ||  Reading murder books
pdp is alive! ||  tryin' to stay hip" - B. Idol
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Re: [Simh] 8" Floppy disk image getting HALT error

[Timothe Litt]

On 11-Jul-17 18:02, Johnny Billquist wrote:
> On 2017-07-11 21:09, Timothe Litt wrote:
>> VMS mount /over=id /foreign is the quickest way to identify files-11 and
>> RT disks.  FILES-11 can be read directly; use EXCHANGE for RT-11.  Once
>> you have the disk mounted on VMS, you can network it to wherever you
>> like.
>
> Similar story if you have RSX. I might have forgotten a thing or two
> about VMS here, but I would have thought /OVER=ID/FOREIGN would not
> then let you access the disk in the direct way if it is Files-11.
I was suggesting the easiest way to IDENTIFY the media.  /FOREIGN will
dump the filesystem type when it looks for a HOM block.  Once you know
that, you use the appropriate command / utility to access that type.

To access FILES-11 on VMS, you don't use /FOREIGN, just mount (though
/over=id will allow a private mount without knowing the volume label.)

MOUNT and EXCHANGE details are available from HELP and the manuals.

VMS has, arguably, the most filesystem support and tools for this.  But
OS choice is a religion.  Use whatever you believe in & have available;
there is no point in arguing religion.

Of course, if the OP is more interested in the result than the process,
he can probably get one of us to extract the one file for him...



smime.p7s
Description: S/MIME Cryptographic Signature
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Re: [Simh] 8" Floppy disk image getting HALT error

[Johnny Billquist]

Hi, Ragge, :-)

On 2017-07-11 23:50, Anders Magnusson wrote:

Den 2017-07-11 kl. 14:29, skrev Johnny Billquist:


To sum things up. You can probably ignore all the questions about if
this really is some DEC floppy, what kind of format it has, and so on.
If kryoflux managed to extract data that looks valid with RX02
parameter settings, then I'd say we can be sure it is an RX02 disk.
And this format was unique to DEC, so it can't be anything else.


Nitpicking:  Sintran had the same format (F-F 12 IIRC) so DEC floppies
could be used by Sintran and vice versa.
The RX02 floppies were pre-formatted by DEC and were quite expensive,
but any floppy could be formatted using Sintran and then used on a VAX
for example :-)


Are you confusing the RX01/RX02 with the RX50 now?
The RX01 is a bog standard IBM format SSSD floppy.
The RX02 is the same as an RX01. DEC just flips a bit in the header of 
each sector, and write the data in double density. So you can always 
easily format back and forth between RX01 and RX02 in the floppies, and 
anyone could do it.


The RX50 on the other hand was preformatted, and in a format that (I 
thought) noone else used. So DEC really had a captive market for that one.


I've used plenty of IBM 8" floppies in RX01 drives... Never had an RX02 
myself, so I could not do the reformatting for that. But look inside any 
DEC OS, and you'll find the command to reformat RX01 as RX02 and back.


Johnny

--
Johnny Billquist  || "I'm on a bus
  ||  on a psychedelic trip
email: b...@softjar.se ||  Reading murder books
pdp is alive! ||  tryin' to stay hip" - B. Idol
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Re: [Simh] 8" Floppy disk image getting HALT error

[Johnny Billquist]

On 2017-07-11 21:09, Timothe Litt wrote:

VMS mount /over=id /foreign is the quickest way to identify files-11 and
RT disks.  FILES-11 can be read directly; use EXCHANGE for RT-11.  Once
you have the disk mounted on VMS, you can network it to wherever you like.


Similar story if you have RSX. I might have forgotten a thing or two 
about VMS here, but I would have thought /OVER=ID/FOREIGN would not then 
let you access the disk in the direct way if it is Files-11.



If you insist on doing things the hard way, there is low-level detail to
worry about.

The first  track on DEC 8" floppies is reserved for boot (but not used)
in the standard RX01/2 formats.  It's not used by any DEC OS.  Not even
for booting (the DEC boot block is the first LBN following the reserved
track.)

Both are 77 tracks, 1 sided, 26 sectors/track.  The rx01 is 128
bytes/sector; the rx02 256.  So an RX01 image will be about 251KB, an
RX02 about 501KB.


Which then makes sense for data to start at track 26.


Logical blocks are 512 bytes; meaning that an LBN consists of 4 or 2
physical sectors.  The physical sectors are interleaved.  If you have a
physical dump of the disk (and your tools haven't outsmarted you), the
easiest thing to do is to de-interleave it.

Use the attached utility, which documents the format & will
interleave/deinterleave a floppy image using the usual interleave rules.

19D0(16) is close to 26 * 256 (short by 48 bytes), so I'd guess you have
an rx02 and are seeing the empty boot track.  (Although not guaranteed,
the track was usually written with all zeroes).


I think Walked was a little careless in his conversion. He said bytes 
0-6655, which actually turns out to be 01A0, or exactly where track 1 
starts.



The 48 bytes may be left over from formatting, or an artifact of how
you're reading the medium.  Or an indication that your recovery dropped
something.  Hopefully it checks the CRCs..


Or just a conversion error. :-)


The E5 is probably left over from formatting.  I think it was part of
the sync pattern, and that the formatter wrote

If you see 8-bit data, it's probably RT11 or Files-11.  These are
self-identifying - block 1 (the second block) will have a filesystem
name in starting at byte 760(8).  Will be DECFILE11A for ODS1 or
DECFILE11B for ODS2, DECRT11A for RT11.  RSTS is also possible - I don't
remember it's code, probably DECRSTS11A.  Given that, data
(deinterleaved), humans can easily tell what you have.


Unfortunately it's not that easy.
Files-11 do indeed have that identifier in block 1. RT-11 however, might 
not. There is no requirement and no checking, and depending on what 
version, and what tool, you might be lucky and find such a string there, 
but the absence don't mean anything.
VMS Exchange helpfully enough actually writes "DECVMSEXCHNG" there. 
(cut-and-pasted from a dump right here and now)
FLX (under RSX) do not write anything at all when you initialize the 
disk with an RT-11 file structure.


I don't have any RSTS/E disk images to quickly peek into.

But with some detective work, you can still figure out if it is an RT-11 
volume.


But the fact that the dump seem to get directly to document data without 
anything at all suggest that there isn't any file structure at all on 
the disk.



RT11 files are contiguous, so recovery is easy.  FILES-11 files can be,
but probably aren't.  You have to read mapping pointers.  There are
tools that will do that (one of these daze I do intend to release mine.)

But it's much easier to just run EXCHANGE and say "COPY" by filename :-)


Indeed. Seems unneccesary work to write a tool to parse that out when 
tools already exist. You can do it in VMS, or RSX, RSTS/E or Ultrix, 
without having to write any code.



As for WPS-8  - yes, it's packed into 12 bits - but it's also encoded (I
vaguely remember it as a 6-bit code with shift & formatting - but I'd
have to look up the code I wrote to translate it.)  In any case, it
would not look like text to a "modern" filesystem.


Yeah. I think we can exclude WPS from likely formats.

Johnny



Have fun.

On 11-Jul-17 13:26, Walker Sampson wrote:

Hi everyone,

Many thanks for this feedback. A fair amount to chew on here. I’ve sent a 
request to the donor to share the disk image, if I get a positive I’ll be happy 
to throw up a Dropbox link to it for others to examine.

This may mean a problematic read of the disk itself, but addresses 0 – 
019D0 are all zeroed out, or about bytes 0 – 6655.

Data begins at byte 6657, and that is the document I mentioned. Last byte of 
the document is 73080 and then just blocks of either zero or E5E5E5E5 till the 
end of the disk.

To Paul’s point of mounting a RK05 drive – which drive should I be mounting here, 
assuming it is the RX02 disk it seems to be? “AT RX01 ” still gets 
a HALT error. Of course, as you all point out, perhaps this isn’t a bootable disk, 
period. “SH RX01” gives “RX1, 256KB, attached to test-decrx01.img, write enabled”

FYI as well, on a 

Re: [Simh] 8" Floppy disk image getting HALT error

[Anders Magnusson]

Den 2017-07-11 kl. 14:29, skrev Johnny Billquist:


To sum things up. You can probably ignore all the questions about if 
this really is some DEC floppy, what kind of format it has, and so on. 
If kryoflux managed to extract data that looks valid with RX02 
parameter settings, then I'd say we can be sure it is an RX02 disk. 
And this format was unique to DEC, so it can't be anything else.


Nitpicking:  Sintran had the same format (F-F 12 IIRC) so DEC floppies 
could be used by Sintran and vice versa.
The RX02 floppies were pre-formatted by DEC and were quite expensive, 
but any floppy could be formatted using Sintran and then used on a VAX 
for example :-)


-- R
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Re: [Simh] 8" Floppy disk image getting HALT error

[Johnny Billquist]

Timothe Litt brought up that track 0 is probably not actually used.
I was just trying to remember that one myself, so there is probably 
your explanation for all the zeroes in the beginning.


Size looks good. An RX01 should be about 128Kbyte, while an RX02 should 
be about 256Kbyte.


To mount it, you should obviously say that it is an RX02. If you try 
RX01, it will also be wrong for various reasons.


Data starting at byte 6657 indicates that it start right up at sector 
26. If there is nothing before, and nothing after the document, that 
makes it sound as if the data was written direct to the disk without any 
file system at all. Definitely nothing bootable in there, or else you'd 
find lots of binary junk before that text.


The zeroes and e5e5e5e5 values seems to just be filler in there.

  Johnny


On 2017-07-11 19:26, Walker Sampson wrote:

Hi everyone,

Many thanks for this feedback. A fair amount to chew on here. I’ve sent a 
request to the donor to share the disk image, if I get a positive I’ll be happy 
to throw up a Dropbox link to it for others to examine.

This may mean a problematic read of the disk itself, but addresses 0 – 
019D0 are all zeroed out, or about bytes 0 – 6655.

Data begins at byte 6657, and that is the document I mentioned. Last byte of 
the document is 73080 and then just blocks of either zero or E5E5E5E5 till the 
end of the disk.

To Paul’s point of mounting a RK05 drive – which drive should I be mounting here, 
assuming it is the RX02 disk it seems to be? “AT RX01 ” still gets 
a HALT error. Of course, as you all point out, perhaps this isn’t a bootable disk, 
period. “SH RX01” gives “RX1, 256KB, attached to test-decrx01.img, write enabled”

FYI as well, on a modern HFS+ system, the disk image file is coming in at 256 
KB.

Any thoughts on the run of zeroes and E5E5E5E5?

Thanks again,

Walker

 On 7/11/17, 6:29 AM, "Simh on behalf of Johnny Billquist" 
 wrote:

Hi.

On 2017-07-10 22:10, Walker Sampson wrote:
> Hi everyone,
>
> Let me preface this by saying that I’m unfamiliar with the original PDP
> machines. I work as a digital archivist and have received 8” floppy
> disks from which I need to recover data.
>
> I believe I have recovered at least partial data from these disks; I’ve
> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk
> controller and gotten positive sector results setting the format to a
> DEC RX02 sector image. When I investigate the resulting disk image in a
> hex editor, I am seeing clearly a report document, so I don’t believe I
> have a false positive.
>
> Outside of observing in a hex editor however, I don’t know how to access
> the disk or its contents. Using SIMH, I haven’t gotten the virtual
> machine to boot the floppy disk image.
>
> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT
> instruction, PC: 02 (HALT)” message for the PDP-11 program. The
> PDP-8 stalls indefinitely and the PDP-10 outputs “Non-existent device”
> as well.
>
> I can’t go back to the donors and ask what machines these 8” floppies
> were used with, so I’m not sure how to begin troubleshooting.
>
> Any advice in that area is much appreciated!
>
> Thanks,
>
>
> Walker

To sum things up. You can probably ignore all the questions about if
this really is some DEC floppy, what kind of format it has, and so on.
If kryoflux managed to extract data that looks valid with RX02 parameter
settings, then I'd say we can be sure it is an RX02 disk. And this
format was unique to DEC, so it can't be anything else.

Which also means, you already have managed to exact all the bits, and
most probably correct. The next question is just about restoring the
data in a more coherent form, which means getting it in the form of
files, and understanding the format of the files.

For this, we need to know what system the floppy was written on. Paul
Koning gave the most useful advice. The first few blocks will usually be
enough to find out what system the floppy was written on.

RX02 floppies could certainly be bootable, but most are not. OS/8 (and
derivatives) for the PDP-8, and RT-11 for the PDP-11 were the ones that
supported RX02 as a bootable system. Other systems supported the
floppes, but only as a way of carrying bits around, so not being able to
boot from the floppy is probably to be expected.

So, if you could give us just the first few blocks, it should be
possible to tell what file system it has, and that gives us OS, file
structure and probably the ability to work out the rest in quick order.

Johnny

--
Johnny Billquist  || "I'm on a bus
   ||  on a psychedelic trip
email: b...@softjar.se ||  Reading murder 

Re: [Simh] 8" Floppy disk image getting HALT error

[khandy21yo]

If you're interested in WPS8 RX50 format, I have a program to READ rX50 images 
and convert the files to Wordperfect format.  
Http://github.com/khandy21yo/emutools.git.  There's other stuff in there, but 
one of the subdirectories contains the source.
It's been some time since I wrote it, so I don't really remember the details.


Sent from my Galaxy Tab® A
 Original message From: Timothe Litt <l...@ieee.org> Date: 
7/11/17  1:09 PM  (GMT-07:00) To: simh@trailing-edge.com Subject: Re: [Simh] 8" 
Floppy disk image getting HALT error 

VMS mount /over=id /foreign is the quickest way to identify
  files-11 and RT disks.  FILES-11 can be read directly; use
  EXCHANGE for RT-11.  Once you have the disk mounted on VMS, you
  can network it to wherever you like.
If you insist on doing things the hard way, there is low-level
  detail to worry about.


The first  track on DEC 8" floppies is reserved for boot (but not
  used) in the standard RX01/2 formats.  It's not used by any DEC
  OS.  Not even for booting (the DEC boot block is the first LBN
  following the reserved track.)


Both are 77 tracks, 1 sided, 26 sectors/track.  The rx01 is 128
  bytes/sector; the rx02 256.  So an RX01 image will be about 251KB,
  an RX02 about 501KB.


Logical blocks are 512 bytes; meaning that an LBN consists of 4
  or 2 physical sectors.  The physical sectors are interleaved.  If
  you have a physical dump of the disk (and your tools haven't
  outsmarted you), the easiest thing to do is to de-interleave it.
Use the attached utility, which documents the format & will
  interleave/deinterleave a floppy image using the usual interleave
  rules.


19D0(16) is close to 26 * 256 (short by 48 bytes), so I'd guess
  you have an rx02 and are seeing the empty boot track.  (Although
  not guaranteed, the track was usually written with all zeroes).


The 48 bytes may be left over from formatting, or an artifact of
  how you're reading the medium.  Or an indication that your
  recovery dropped something.  Hopefully it checks the CRCs..


The E5 is probably left over from formatting.  I think it was
  part of the sync pattern, and that the formatter wrote 


If you see 8-bit data, it's probably RT11 or Files-11.  These are
  self-identifying - block 1 (the second block) will have a
  filesystem name in starting at byte 760(8).  Will be DECFILE11A
  for ODS1 or DECFILE11B for ODS2, DECRT11A for RT11.  RSTS is also
  possible - I don't remember it's code, probably DECRSTS11A.  Given
  that, data (deinterleaved), humans can easily tell what you have.


RT11 files are contiguous, so recovery is easy.  FILES-11 files
  can be, but probably aren't.  You have to read mapping pointers. 
  There are tools that will do that (one of these daze I do intend
  to release mine.)
But it's much easier to just run EXCHANGE and say "COPY" by filename
:-)



As for WPS-8  - yes, it's packed into 12 bits - but it's also
encoded (I vaguely remember it as a 6-bit code with shift &
formatting - but I'd have to look up the code I wrote to translate
it.)  In any case, it would not look like text to a "modern"
filesystem.

Have fun.



On 11-Jul-17 13:26, Walker Sampson
  wrote:



  Hi everyone,

Many thanks for this feedback. A fair amount to chew on here. I’ve sent a 
request to the donor to share the disk image, if I get a positive I’ll be happy 
to throw up a Dropbox link to it for others to examine.

This may mean a problematic read of the disk itself, but addresses 0 – 
019D0 are all zeroed out, or about bytes 0 – 6655. 

Data begins at byte 6657, and that is the document I mentioned. Last byte of 
the document is 73080 and then just blocks of either zero or E5E5E5E5 till the 
end of the disk. 

To Paul’s point of mounting a RK05 drive – which drive should I be mounting 
here, assuming it is the RX02 disk it seems to be? “AT RX01 ” still 
gets a HALT error. Of course, as you all point out, perhaps this isn’t a 
bootable disk, period. “SH RX01” gives “RX1, 256KB, attached to 
test-decrx01.img, write enabled”

FYI as well, on a modern HFS+ system, the disk image file is coming in at 256 
KB.

Any thoughts on the run of zeroes and E5E5E5E5? 

Thanks again,

Walker

 On 7/11/17, 6:29 AM, "Simh on behalf of Johnny Billquist" 
<simh-boun...@trailing-edge.com on behalf of b...@softjar.se> wrote:

Hi.

On 2017-07-10 22:10, Walker Sampson wrote:
> Hi everyone,
> 
> Let me preface this by saying that I’m unfamiliar with the original PDP 
> machines. I work as a digital archivist and have received 8” floppy 
> disks from which I need to recover data.
> 
> I believe I have recovered at leas

Re: [Simh] 8" Floppy disk image getting HALT error

[Leo Broukhis]

I think that the proper image size should be 256256, as 6656 is exactly
256x26, w which is a multiple of 13, as well as 256256.

On floppy disks with 77 tracks of 26 128-byte sectors each, or 13 256-byte
sectors, track 0 could be treated as the last one when the media was
accessed at the application level (probably because it tended to be less
reliable due to the heads spending more time there).

Moreover, as the media size is not a multiple of 512, reading the last one
or two sectors may be problematic in some systems if the system block size
is 512. This hindered my recovering of the Terak boot disk for several
years.


Leo


On Jul 11, 2017 10:26 AM, "Walker Sampson" 
wrote:

Hi everyone,

Many thanks for this feedback. A fair amount to chew on here. I’ve sent a
request to the donor to share the disk image, if I get a positive I’ll be
happy to throw up a Dropbox link to it for others to examine.

This may mean a problematic read of the disk itself, but addresses 0 –
019D0 are all zeroed out, or about bytes 0 – 6655.

Data begins at byte 6657, and that is the document I mentioned. Last byte
of the document is 73080 and then just blocks of either zero or E5E5E5E5
till the end of the disk.

To Paul’s point of mounting a RK05 drive – which drive should I be mounting
here, assuming it is the RX02 disk it seems to be? “AT RX01 ”
still gets a HALT error. Of course, as you all point out, perhaps this
isn’t a bootable disk, period. “SH RX01” gives “RX1, 256KB, attached to
test-decrx01.img, write enabled”

FYI as well, on a modern HFS+ system, the disk image file is coming in at
256 KB.

Any thoughts on the run of zeroes and E5E5E5E5?

Thanks again,

Walker

 On 7/11/17, 6:29 AM, "Simh on behalf of Johnny Billquist" <
simh-boun...@trailing-edge.com on behalf of b...@softjar.se> wrote:

Hi.

On 2017-07-10 22:10, Walker Sampson wrote:
> Hi everyone,
>
> Let me preface this by saying that I’m unfamiliar with the original
PDP
> machines. I work as a digital archivist and have received 8” floppy
> disks from which I need to recover data.
>
> I believe I have recovered at least partial data from these disks;
I’ve
> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk
> controller and gotten positive sector results setting the format to a
> DEC RX02 sector image. When I investigate the resulting disk image in
a
> hex editor, I am seeing clearly a report document, so I don’t believe
I
> have a false positive.
>
> Outside of observing in a hex editor however, I don’t know how to
access
> the disk or its contents. Using SIMH, I haven’t gotten the virtual
> machine to boot the floppy disk image.
>
> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT
> instruction, PC: 02 (HALT)” message for the PDP-11 program. The
> PDP-8 stalls indefinitely and the PDP-10 outputs “Non-existent device”
> as well.
>
> I can’t go back to the donors and ask what machines these 8” floppies
> were used with, so I’m not sure how to begin troubleshooting.
>
> Any advice in that area is much appreciated!
>
> Thanks,
>
>
> Walker

To sum things up. You can probably ignore all the questions about if
this really is some DEC floppy, what kind of format it has, and so on.
If kryoflux managed to extract data that looks valid with RX02 parameter
settings, then I'd say we can be sure it is an RX02 disk. And this
format was unique to DEC, so it can't be anything else.

Which also means, you already have managed to exact all the bits, and
most probably correct. The next question is just about restoring the
data in a more coherent form, which means getting it in the form of
files, and understanding the format of the files.

For this, we need to know what system the floppy was written on. Paul
Koning gave the most useful advice. The first few blocks will usually be
enough to find out what system the floppy was written on.

RX02 floppies could certainly be bootable, but most are not. OS/8 (and
derivatives) for the PDP-8, and RT-11 for the PDP-11 were the ones that
supported RX02 as a bootable system. Other systems supported the
floppes, but only as a way of carrying bits around, so not being able to
boot from the floppy is probably to be expected.

So, if you could give us just the first few blocks, it should be
possible to tell what file system it has, and that gives us OS, file
structure and probably the ability to work out the rest in quick order.

Johnny

--
Johnny Billquist  || "I'm on a bus
   ||  on a psychedelic trip
email: b...@softjar.se ||  Reading murder books
pdp is alive! ||  tryin' to stay hip" - B. Idol
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Re: [Simh] 8" Floppy disk image getting HALT error

[Walker Sampson]

Hi everyone,

Many thanks for this feedback. A fair amount to chew on here. I’ve sent a 
request to the donor to share the disk image, if I get a positive I’ll be happy 
to throw up a Dropbox link to it for others to examine.

This may mean a problematic read of the disk itself, but addresses 0 – 
019D0 are all zeroed out, or about bytes 0 – 6655. 

Data begins at byte 6657, and that is the document I mentioned. Last byte of 
the document is 73080 and then just blocks of either zero or E5E5E5E5 till the 
end of the disk. 

To Paul’s point of mounting a RK05 drive – which drive should I be mounting 
here, assuming it is the RX02 disk it seems to be? “AT RX01 ” still 
gets a HALT error. Of course, as you all point out, perhaps this isn’t a 
bootable disk, period. “SH RX01” gives “RX1, 256KB, attached to 
test-decrx01.img, write enabled”

FYI as well, on a modern HFS+ system, the disk image file is coming in at 256 
KB.

Any thoughts on the run of zeroes and E5E5E5E5? 

Thanks again,

Walker

 On 7/11/17, 6:29 AM, "Simh on behalf of Johnny Billquist" 
 wrote:

Hi.

On 2017-07-10 22:10, Walker Sampson wrote:
> Hi everyone,
> 
> Let me preface this by saying that I’m unfamiliar with the original PDP 
> machines. I work as a digital archivist and have received 8” floppy 
> disks from which I need to recover data.
> 
> I believe I have recovered at least partial data from these disks; I’ve 
> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk 
> controller and gotten positive sector results setting the format to a 
> DEC RX02 sector image. When I investigate the resulting disk image in a 
> hex editor, I am seeing clearly a report document, so I don’t believe I 
> have a false positive.
> 
> Outside of observing in a hex editor however, I don’t know how to access 
> the disk or its contents. Using SIMH, I haven’t gotten the virtual 
> machine to boot the floppy disk image.
> 
> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT 
> instruction, PC: 02 (HALT)” message for the PDP-11 program. The 
> PDP-8 stalls indefinitely and the PDP-10 outputs “Non-existent device” 
> as well.
> 
> I can’t go back to the donors and ask what machines these 8” floppies 
> were used with, so I’m not sure how to begin troubleshooting.
> 
> Any advice in that area is much appreciated!
> 
> Thanks,
> 
> 
> Walker

To sum things up. You can probably ignore all the questions about if 
this really is some DEC floppy, what kind of format it has, and so on. 
If kryoflux managed to extract data that looks valid with RX02 parameter 
settings, then I'd say we can be sure it is an RX02 disk. And this 
format was unique to DEC, so it can't be anything else.

Which also means, you already have managed to exact all the bits, and 
most probably correct. The next question is just about restoring the 
data in a more coherent form, which means getting it in the form of 
files, and understanding the format of the files.

For this, we need to know what system the floppy was written on. Paul 
Koning gave the most useful advice. The first few blocks will usually be 
enough to find out what system the floppy was written on.

RX02 floppies could certainly be bootable, but most are not. OS/8 (and 
derivatives) for the PDP-8, and RT-11 for the PDP-11 were the ones that 
supported RX02 as a bootable system. Other systems supported the 
floppes, but only as a way of carrying bits around, so not being able to 
boot from the floppy is probably to be expected.

So, if you could give us just the first few blocks, it should be 
possible to tell what file system it has, and that gives us OS, file 
structure and probably the ability to work out the rest in quick order.

Johnny

-- 
Johnny Billquist  || "I'm on a bus
   ||  on a psychedelic trip
email: b...@softjar.se ||  Reading murder books
pdp is alive! ||  tryin' to stay hip" - B. Idol
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Re: [Simh] 8" Floppy disk image getting HALT error

[Kevin Handy]

If it is readable as text, it probably isn't wps-8. At least the 5-1/4"
formar was encoded into 12 bit words, and weren't directly readable.

On Mon, Jul 10, 2017 at 5:01 PM, Tom Morris  wrote:

> In addition to everything mentioned by everyone else, you might want to
> take into account the type of "report" that you saw. If it's more a
> document type report than a line printer listing report, you might have a
> diskette from a DEC WPS-8 word processing system.
>
> https://en.wikipedia.org/wiki/WPS-8
>
> Tom
>
> On Mon, Jul 10, 2017 at 4:10 PM, Walker Sampson <
> walker.samp...@colorado.edu> wrote:
>
>> Hi everyone,
>>
>>
>>
>> Let me preface this by saying that I’m unfamiliar with the original PDP
>> machines. I work as a digital archivist and have received 8” floppy disks
>> from which I need to recover data.
>>
>>
>>
>> I believe I have recovered at least partial data from these disks; I’ve
>> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk controller
>> and gotten positive sector results setting the format to a DEC RX02 sector
>> image. When I investigate the resulting disk image in a hex editor, I am
>> seeing clearly a report document, so I don’t believe I have a false
>> positive.
>>
>>
>>
>> Outside of observing in a hex editor however, I don’t know how to access
>> the disk or its contents. Using SIMH, I haven’t gotten the virtual machine
>> to boot the floppy disk image.
>>
>>
>>
>> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT
>> instruction, PC: 02 (HALT)” message for the PDP-11 program. The PDP-8
>> stalls indefinitely and the PDP-10 outputs “Non-existent device” as well.
>>
>>
>>
>> I can’t go back to the donors and ask what machines these 8” floppies
>> were used with, so I’m not sure how to begin troubleshooting.
>>
>>
>>
>> Any advice in that area is much appreciated!
>>
>>
>>
>> Thanks,
>>
>>
>> Walker
>>
>>
>>
>>
>>
>> ___
>> Simh mailing list
>> Simh@trailing-edge.com
>> http://mailman.trailing-edge.com/mailman/listinfo/simh
>>
>
>
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>
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Re: [Simh] 8" Floppy disk image getting HALT error

[Tom Morris]

In addition to everything mentioned by everyone else, you might want to
take into account the type of "report" that you saw. If it's more a
document type report than a line printer listing report, you might have a
diskette from a DEC WPS-8 word processing system.

https://en.wikipedia.org/wiki/WPS-8

Tom

On Mon, Jul 10, 2017 at 4:10 PM, Walker Sampson  wrote:

> Hi everyone,
>
>
>
> Let me preface this by saying that I’m unfamiliar with the original PDP
> machines. I work as a digital archivist and have received 8” floppy disks
> from which I need to recover data.
>
>
>
> I believe I have recovered at least partial data from these disks; I’ve
> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk controller
> and gotten positive sector results setting the format to a DEC RX02 sector
> image. When I investigate the resulting disk image in a hex editor, I am
> seeing clearly a report document, so I don’t believe I have a false
> positive.
>
>
>
> Outside of observing in a hex editor however, I don’t know how to access
> the disk or its contents. Using SIMH, I haven’t gotten the virtual machine
> to boot the floppy disk image.
>
>
>
> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT
> instruction, PC: 02 (HALT)” message for the PDP-11 program. The PDP-8
> stalls indefinitely and the PDP-10 outputs “Non-existent device” as well.
>
>
>
> I can’t go back to the donors and ask what machines these 8” floppies were
> used with, so I’m not sure how to begin troubleshooting.
>
>
>
> Any advice in that area is much appreciated!
>
>
>
> Thanks,
>
>
> Walker
>
>
>
>
>
> ___
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> Simh@trailing-edge.com
> http://mailman.trailing-edge.com/mailman/listinfo/simh
>
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Re: [Simh] 8" Floppy disk image getting HALT error

[Ethan Dicks]

On Mon, Jul 10, 2017 at 4:36 PM, Clem Cole  wrote:
> Paul - offered great info.   First are your sure these came from DEC
> systems?  8" floppies were originally developed (by IBM to load microcode on
> the 3330 disks) years before DEC started to use them.

Yep, but if they are RX02 format (single-density headers,
double-density data), then they can only be from a DEC system.

>   IIRC DEC only used them on PDP-8's and 11s.

Not strictly true.

> The Vaxen and PDP-10 actually connected to a PDP-11 front end that actually 
> controlled them.

Many VAXen, 11/780s and similar, did have a console RX01 attached via
a console PDP-11, but you were free to stuff an RX11 into a Unibus
slot and read floppies directly from VMS, for example.  It was
uncommon, I'll grant you, but it was done.  There was a pair of
11/750s at OSU, Scarlet and Grey, used in the Engineering Graphics
140-series in the mid-1980s that used student-accessible RX01 drives
for saving their work.  Uncommon, but possible.

> Second, as Paul said, trying to boot from them, unless you know what you are
> doing is likely to cause a certain amount of madness, be a tad random.

Yep.

> when dealing with floppies, you have to remember two important things
> format (hard or soft) and interleave.Early [8" in particular] used hard
> formatting.   I don't think DEC's version of the 8" ever did [ Paul is more
> likely to remember that type of factoid].

Nope.  They did not.

>> I can’t go back to the donors and ask what machines these 8” floppies were
>> used with, so I’m not sure how to begin troubleshooting.

I would start by attempting to read them as RX01.  That low-level
format is identical to IBM 3740 format and covers a wide range of
single-density machines.  If it really reads successfully as a 500KB
RX02, then it's a DEC RX02 and likely nothing else.

Grubbing around the resulting image file with hex or octal dumps,
especially on the first track, will likely reveal what sort of system
it's from.  If the source is DEC, it's most likely to be PDP-8 or
PDP-11, but I happen to have a few diskettes from a 3rd-party disk
system that, while it was on either a PDP-11 or PDP-8 (the labels in
my case are helpful), they are *not* RX01 or RX02 compatible.  DSD
drives were semi-common for some cost-conscious DEC users, and while a
Kryoflux can certainly be told how to read them, it won't be with
either an RX01 or RX02 description file.

Again, if you get meaningful sectors out of an RX01-formatted read,
I'd start there.  The IBM 3740 format was widely used.  If that turns
up garbage, then it's a harder hunt for a match.

-ethan
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Re: [Simh] 8" Floppy disk image getting HALT error

[Al Kossow]

On 7/10/17 1:10 PM, Walker Sampson wrote:
> positive sector results setting the format to a DEC RX02 sector image. When I
> investigate the resulting disk image in a hex editor, I am seeing clearly a 
> report document

Well that narrows it down a great deal.
As others have said, you still don't know if it is bootable, what operating 
system it was
written by, or what software on that system wrote it.

If you are serious about recovering the contents, I would suggest contacting 
Chuck Guzis
at Sydex, who has extensive experience doing commercial floppy data recovery




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Re: [Simh] 8" Floppy disk image getting HALT error

[Clem Cole]

Paul - offered great info.   First are your sure these came from DEC
systems?  8" floppies were originally developed (by IBM to load microcode
on the 3330 disks) years before DEC started to use them.   IIRC DEC only
used them on PDP-8's and 11s.   The Vaxen and PDP-10 actually connected to
a PDP-11 front end that actually controlled them.

Second, as Paul said, trying to boot from them, unless you know what you
are doing is likely to cause a certain amount of madness, be a tad random.
   The trick would be to use the KryoFlux to get and image of the bits and
then start to work out from there what it is from the first we blocks.

Two more very important points 

when dealing with floppies, you have to remember two important things
format (hard or soft) and interleave.Early [8" in particular] used hard
formatting.   I don't think DEC's version of the 8" ever did [ Paul is more
likely to remember that type of factoid].  With hard formatting you at
least know the number of sectors in each 'ring' - but you don't know how
the SW interleaved them.  Different systems interleaved in different ways.

The KryoFlux has to have some way to handle all of this but its going to be
important to know as much as we can about who the SW was configured when we
try too decode the first we blocks.   So you need to tell folks as much as
you can about how the data came off the disk when you grab it.

Good luck.

On Mon, Jul 10, 2017 at 4:16 PM, Paul Koning  wrote:

> PDP-11 disks are not necessarily bootable.  If they aren't, attempting to
> do so may just give you a halt, or spurious behavior.  Some systems
> initialize non-bootable disks with a dummy bootstrap that tells you "this
> is not a bootable disk", but you can't necessarily count on that.
>
> Apart from that, you attached an RK05 drive, so if you gave it your RX01
> image that can't work right because an RK05 is a very different device
> (4800 512-byte sectors).
>
> Several operating systems support RX01 and/or RX02.  The first few sectors
> of the disk will give a clue which OS you have (or more precisely, which
> file system layout, which is tied to the OS).  If you can post the disk
> image in some place where people can see it, you're likely to get some
> help.  If that's not an option but you can post the first 5 sectors or so
> as hex dumps, the file system type and thus the OS you'd need to interpret
> the contents is likely to become clear.
>
> paul
>
> On Jul 10, 2017, at 4:10 PM, Walker Sampson  > wrote:
>
> Hi everyone,
>
> Let me preface this by saying that I’m unfamiliar with the original PDP
> machines. I work as a digital archivist and have received 8” floppy disks
> from which I need to recover data.
>
> I believe I have recovered at least partial data from these disks; I’ve
> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk controller
> and gotten positive sector results setting the format to a DEC RX02 sector
> image. When I investigate the resulting disk image in a hex editor, I am
> seeing clearly a report document, so I don’t believe I have a false
> positive.
>
> Outside of observing in a hex editor however, I don’t know how to access
> the disk or its contents. Using SIMH, I haven’t gotten the virtual machine
> to boot the floppy disk image.
>
> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT
> instruction, PC: 02 (HALT)” message for the PDP-11 program. The PDP-8
> stalls indefinitely and the PDP-10 outputs “Non-existent device” as well.
>
> I can’t go back to the donors and ask what machines these 8” floppies were
> used with, so I’m not sure how to begin troubleshooting.
>
> Any advice in that area is much appreciated!
>
> Thanks,
>
> Walker
>
>
> ___
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>
>
>
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Re: [Simh] 8" Floppy disk image getting HALT error

[Paul Koning]

PDP-11 disks are not necessarily bootable.  If they aren't, attempting to do so 
may just give you a halt, or spurious behavior.  Some systems initialize 
non-bootable disks with a dummy bootstrap that tells you "this is not a 
bootable disk", but you can't necessarily count on that.

Apart from that, you attached an RK05 drive, so if you gave it your RX01 image 
that can't work right because an RK05 is a very different device (4800 512-byte 
sectors).

Several operating systems support RX01 and/or RX02.  The first few sectors of 
the disk will give a clue which OS you have (or more precisely, which file 
system layout, which is tied to the OS).  If you can post the disk image in 
some place where people can see it, you're likely to get some help.  If that's 
not an option but you can post the first 5 sectors or so as hex dumps, the file 
system type and thus the OS you'd need to interpret the contents is likely to 
become clear.

paul

> On Jul 10, 2017, at 4:10 PM, Walker Sampson  
> wrote:
> 
> Hi everyone,
>  
> Let me preface this by saying that I’m unfamiliar with the original PDP 
> machines. I work as a digital archivist and have received 8” floppy disks 
> from which I need to recover data.
>  
> I believe I have recovered at least partial data from these disks; I’ve 
> connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk controller and 
> gotten positive sector results setting the format to a DEC RX02 sector image. 
> When I investigate the resulting disk image in a hex editor, I am seeing 
> clearly a report document, so I don’t believe I have a false positive.
>  
> Outside of observing in a hex editor however, I don’t know how to access the 
> disk or its contents. Using SIMH, I haven’t gotten the virtual machine to 
> boot the floppy disk image.
>  
> Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT 
> instruction, PC: 02 (HALT)” message for the PDP-11 program. The PDP-8 
> stalls indefinitely and the PDP-10 outputs “Non-existent device” as well. 
>  
> I can’t go back to the donors and ask what machines these 8” floppies were 
> used with, so I’m not sure how to begin troubleshooting.
>  
> Any advice in that area is much appreciated!
>  
> Thanks,
> 
> Walker
>  
>  
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[Simh] 8" Floppy disk image getting HALT error

[Walker Sampson]

Hi everyone,

Let me preface this by saying that I’m unfamiliar with the original PDP 
machines. I work as a digital archivist and have received 8” floppy disks from 
which I need to recover data.

I believe I have recovered at least partial data from these disks; I’ve 
connected a Y-E Data 8” floppy drive to a KryoFlux floppy disk controller and 
gotten positive sector results setting the format to a DEC RX02 sector image. 
When I investigate the resulting disk image in a hex editor, I am seeing 
clearly a report document, so I don’t believe I have a false positive.

Outside of observing in a hex editor however, I don’t know how to access the 
disk or its contents. Using SIMH, I haven’t gotten the virtual machine to boot 
the floppy disk image.

Commands “AT RK01 ” and then “BOOT RK01” give me a “HALT 
instruction, PC: 02 (HALT)” message for the PDP-11 program. The PDP-8 
stalls indefinitely and the PDP-10 outputs “Non-existent device” as well.

I can’t go back to the donors and ask what machines these 8” floppies were used 
with, so I’m not sure how to begin troubleshooting.

Any advice in that area is much appreciated!

Thanks,

Walker


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