On Mon, Jul 17, 2023, 10:59 AM Ethan Dicks via cctalk <cctalk@classiccmp.org> wrote:
> On Mon, Jul 17, 2023 at 12:48 PM Ethan Dicks <ethan.di...@gmail.com> > wrote: > > 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. > 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 >
