[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 <Walker.Sampson at 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 <disk_image>” and then “BOOT RK01” give me a “HALT instruction, PC: 000002 (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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