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IMD can't read 250kHz disk in 360K drive

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    Yes and yes.


      Alignment is the only thing that I can think of then. Perhaps the originals are a couple of mills offset from the orientation of the drive used to write the originals. You should certainly be able to see some sectors in any case.


        Out of curiosity, what brand/models are each of the drives?

        Here is an experiment you can try to see if this is the index "blind spot" that chuck is taking about.

        For this experiment, we can't use ImageDisk, as it craps itself if it can not see the index during its analysis phase. Instead, lets use Trixter's disk2img .

        Take one of your disks that was formatted in the Kaypro. Cut a small sticky square from a post-it note and carefully pace it over the jacket's index opening. (You don't want it sticking to the cookie). Then use disk2img to read in the image. Since it is not a DOS disk, you will need to manually specify the heads/sectors/tracks. Something like "disk2img b: test.img /t40 /s10 /h2

        If it succeeds, try removing the piece of post-it note and see if it now fails. If that happens, then it is the "blind spot". If both fail, then it is something else such as alignment.


          The system is a PC/AT 5170 with its stock drives. Drive A is a 1.2M and Drive B is a 360K with the asterisk in the corner. I'll try the test tonight!


            If IMD saw no sectors at all, it's not the index problem. Typically, if sectors are numbered 1-10 on the track, the "blind spot" would have IMD seeing sectors 2-10. You might also try Anadisk.

            But the symptom of "it used to see data on the disk, but now it doesn't" usually indicates a dirty head. Can happen quite a bit if you're using old media. Same for tapes.
            Last edited by Chuck(G); May 11, 2021, 01:24 PM.


              Chuck - IMD sometimes see sectors, more often than not it does, but on occasion it doesn't.

              SomeGuy - both tests fail on drive B:, covered or uncovered. I tested drive A: (1.2M) and it reads it with no tape (it kept trying to reread one sector), but fails with tape over the hole.

              22disk works on it though. I can dtoc a 300K+ file, then ctod a file, and comparing both files matches.


                I suspect that IMD attempts to get the layout by issuing a READ TRACK, which waits for the index hole, then reads sector IDs from that point. I'm guessing; I haven't looked at the IMD code for several years.

                Why 22Disk works, but IMD doesn't is anyone's guess. I'll see if I can find an alternative to IMD for copying files.


                  teledisk reads it in the 360K drive. It says "head id 0 differs from physical" DSDD interleave 3:1 sector size 512, sid 0 sect ids 0-9, side 1 sect ids 10-19

                  teledisk reads it in the 1.2M drive, but also keeps saying interleave changed to 4:1, 3:1, 4:1, and so on.

                  I tried imd 1.17 to read disk b: again, it says:

                  0/0 unable to determine interleave
                  300k dd - 9 sectors of 512 bytes - g1:24 g2:64
                  read error (8 ) noadrmark - reanalyzing
                  300k dd - 8 sectors of 512 bytes - g1:27 g2:58
                  read error (8 ) nodata - unavailable
                  read errir (4) noadrmark - unavailable
                  read errir (7) noadrmark - unavailable
                  read errir (5) noadrmark - unavailable
                  read errir (9) noadrmark - unavailable
                  read errir (3) noadrmark - unavailable
                  read errir (6) noadrmark - unavailable
                  read errir (2) noadrmark - unavailable
                  0/1 250k dd - 10 sectors of 512 bytes - g1:7 g2:14
                  single step
                  1/0 read error (8 ) noadrmark - reanalyzing
                  10 sectors (4 compressed, 8 unavailable)


                    I did discover something interesting with IMD - reading a Kaypro (22DISK KAY2) floppy in a a 360K drive attached to a secondary controller appears to read just fine, but the resulting image file is garbage. 22Disk on the same setup works just fine.

                    Glad that IMD isn't mine...


                      "side 0 sect ids 0-9, side 1 sect ids 10-19" well, that won't work with Disk2img. That assumes sectors number 1 through x on both sides. Guess I should have looked that format up first. So, it looks like Teledisk works fine.

                      As for ImageDisk... "300k dd - 9 sectors of 512 bytes - g1:24 g2:64"?

                      300kbps in the 360k drive? No wonder it is returning garbage. ImageDisk is doing something horribly wrong if it is detecting 300kbps here. (Of course, on the 1.2mb drive, double density 300kbps is normal)

                      ImageDisk has a command line parameter that claims it will lock the data rate. Perhaps try launching Imagedisk with the parameter "LR=250"


                        It keeps spinning through 250-300-500 when it is trying to determine what the first track is. Should it? Should I check the drive config in setup? Maybe I should.

                        I'll try the LR=250.


                          LR=250 works!!!!


                            Well, that's why 22Disk works--it differentiates drive types. None of this silly "you need to disable double-stepping" garbage.


                              Nice. So it looks like there is just the perfect combination of minor issues (probably drive speed and analog signal filtering) that throws off ImageDisk.

                              The thing about ImageDisk is it does not make any assumptions about the drive type. For example, this is why one always has to specify single/double stepping every time. Sometimes this is beneficial, other times it is a headache.

                              I'm not exactly sure how ImageDisk does its analysis, but it looks as if at least in one pass it may start with 500kbps then works its way down to 300 and then 250. If it cared about the drive type, it should at least try 250 first. In this case the wind is blowing in just the right direction to make something vaguely detectable at 300kbps.


                                I agree; it seems ImageDisk makes no assumptions about anything and really counts on the user to configure it. If you know all of its tricks you can probably get the most out of it, but for me it usually fails and I had no idea I had to set a translate setting or something. Thanks everyone for helping me figure it out!!!