17 Jul
2023
17 Jul
'23
5:16 p.m.
On Mon, Jul 17, 2023, 10:59 AM Ethan Dicks via cctalk <cctalk(a)classiccmp.org
wrote:
On Mon, Jul 17, 2023 at 12:48 PM Ethan Dicks
<ethan.dicks(a)gmail.com
wrote:
I've encountered this with Rainbow disks. I have a logical to phys
conversion program.
Also when i wrote the impdrive driver for the rainbow: you have to do the
unmapping
the Z80 code would do to make the 3.5" 720k floppy work in the Rainbow.
The physical sectors are numbered 1-10 on the drive (maybe past track 0 and
1). And
it is 1-10, there is no sector 0. These sectors refer to the logical
sectors 1, 3, 5, 7, 9, 2, 4,
6, 8 ,10. My program filters the 'physical' disk into a 'logical' oneso
that mtools can read
the FAT contained on my MS-DOS disks. On the Rainbow, at least, the WD
floppy controller
didn't mess with the sectors, so the interleave was done at the lowest
levels of whatever
OS' floppy driver.
Chances are quite good that there's a mismatch somewhere. If you always
read in one way and
write in that same way, it works (eg, both ends agree). Sometimes you need
to convert from one
to the other, which I always have to do via trial and error.
For Venix, there was a different interleave (because of course there is),
so there may be some
experimenting that's needed. But since it is Unix, I suspect Ultrix may
have its own interleave,
but who knows. I've not looked at the source.
I believe I've uploaded these to github, but can't find them at the moment.
I can look if people
want. This may be all that's needed. It's been handy for both DOS and Venix
disks I've had to
decode.
Warner
On Mon, Jul 17, 2023 at 12:28 PM Henry Bent via
cctalk
> I'm almost thoroughly unfamiliar with IMD - is there some obvious
> extraction/conversion option that I am missing here?
As mentioned previously, yes. There's an additional step that has to
happen to any direct imaging of RX50 disks. John Wilson's PUTR
happens to do this convolution internally.
If you desire is to snapshot physical media for rewriting later, IMD
is excellent. If you want logical-block-order files for simh, you
need one more step (keep reading).
Were these disks actually imaged correctly? I
would appreciate any
suggestions.
Yes they were.
From: http://www.chdickman.com/pdp11/pro380.txt
"The RX50 floppy starts at track 1. Track 0 is logically placed after
track 79. The sectors are interleaved 1, 3, 5, 7, 9, 0, 2, 4, 6, 8,
10. The track shift and interleave must be taken into account when
moving disks between real PDP-11 and emulators."
I have had good luck with a secfor convolver from the same page as this
comment:
http://www.chdickman.com/pdp11/lbn2rx50.c
It will go both ways, to and from physical block order and logical block
order.