On Wed, Aug 11, 2021 at 5:59 PM Paul Koning <paulkon...@comcast.net> wrote: > > > On Aug 11, 2021, at 7:06 PM, Fritz Mueller via cctalk > > <cctalk@classiccmp.org> wrote: > > > >> ... > > > > Ah ha! Thanks much, Glen! > > > > simh is usually pretty good about padding out attached images, > > No, I don't think that is true. What is true is that recent versions of SIMH > will create full size container files for disk containers. But sufficiently > old versions did not, so it is not too strange to run into, say, an RK05 > image that's shorter than 4800 blocks. > > But those normally work; all that happens is that reading too far either > gives you zeroes or a read error, I don't remember which. Since the blocks > were never written they should be marked as unused in the file system and > nothing will read them, so that's fine. > > If there's an unused track at the start of a SIMH image file and in your copy > that was missing, that's a different case. Is that the issue? > > Or is the RX02 emulation different from regular disks? > > paul
It's been a while since the last time I did anything with a SIMH PDP-11. I just fired up the simh-4.0-Current--2020-06-09-0912a927 version that I last used to take a look at these RX-02 disk images. As far as I can tell by default PUTR expects to work with logical sector order RX-02 disk images that are 512,512 bytes in size. The BASIC-11 RX-02 disk image available here is in logical sector order, but is less than 512,512 bytes in size: http://www.bitsavers.org/bits/DEC/pdp11/floppyimages/rx02/ PUTR appears to be unhappy with the disk image unless it is padded to 512,512 bytes in size. On the other hand as far as I can tell by default SIMH expects to work with physical sector order RX-02 disk images. If I mount the logical sector order RX-02 disk image that works with PUTR in SIMH, then RT-11 gives a "?DIR-F-Invalid directory" error. If I translate the logical sector order RX-02 disk image back into a physical sector order disk image (dealing with track shifting, sector interleaving, and track to track sector skewing) then RT-11 on SIMH is happy with the disk image.
