Announcement

Collapse

Forum etiquette

Our mission ...

This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


"PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

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

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

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

    I formatted a couple of disks on my Kaypro 4/83 and wanted to read them in using IMD on my PC/AT. The format is 10 sectors * 512 bytes per sector, 40 tracks.

    I can read the disks using the 1.2M drive A: on the AT, but not the 360K drive B: on it. My Compaq can also read it with its 1.2M drive. When trying to read it in the 360K drive, it doesn't guess the first track properly and then has errors unlike the other 1.2M drives read it. I have written images to the 360K drive and used them on the Kaypro so I can write images to it, but not read them. Any ideas?

    #2
    A couple of things come to mind. First set the BIOS for Drive A to be 360K. Then start IMD and use "S" for settings.
    Set A for 40 tracks, Double Sided, Double Step=ON, and Full analysis.

    Try formatting the floppy to see if it formats properly. There is also a "TESTFDC" program included in Dave Dunfield's
    Utility software. Run that to see that your Floppy Disk Controller (FDC) passes the proper tests. Plus you can run
    the RPM test in IMD ( ver 1.18 ) to make sure it's at 300 RPM.

    Larry

    Comment


      #3
      The A: 1.2M drive does work, it is the B: drive that doesn't read, I tried changing it to B:, 40 tracks, double step off, full analysis on or off.

      Comment


        #4
        But, Don't you want a 40 track Floppy when finished? For an 80 Track drive you set Doublestep=OFF to get 80 full steps, and for a 40 track
        Floppy as a written floppy you set Doublestep=ON to do two steps for every 40 tracks.

        It could be the B: drive that doesn't work correctly is a bit out of alignment. Try formatting it as a 40 Track, copy some image to it, then
        read that image back in, and do a binary compare of the two files.

        Larry

        Comment


          #5
          I was wanting to be able to both read and write using the 360K drive. It seems to be able to write, but if I wanted to read a disk for others to use, it would seem to be the one to use. I _can_ read a 40 track disk in the 1.2M drive, but at 300kHz and not 250kHz, so would that be a properly archived disk since it was sampled at the wrong speed because of the HD drive? Everything I've written on the 360K/B: drive has been readable with the unaltered alignment 360K drive on the Kaypro and other PC drives I have. I saw a note in imagedisk about it being too fast RPM and that sometimes a bit slower can fix things, like 290 rpm or something, but I'm not sure I want to try that.

          Comment


            #6
            What precisely does ImageDisk say when it tries to analyze and read the disk?

            Ideally I'd dump the problematic disk in the problematic drive with a Kryoflux/SCP, which should reveal what is really going on on the disk surface.

            It is possible to write back a 250kbps IMD disk read in at 300kbps using the "translation" setting. But that does get annoying. The included IMDU tool is supposed to be able to alter this setting in an IMD file, but I seem to recall having problems with that the last time I tried it.

            In practice, 10 sectors of 512 bytes per track is a little crowded on each track, so speed issues are a little more likely to affect it. I would at least check the drives both on the PC and the Kaypro to see what the RPM rate currently is.

            Of course, there could be a number of other odd issues at play here. If you have not already done so, try different disks, and clean all the drive heads.

            I think what you are trying to do really SHOULD work as-is.

            Comment


              #7
              >What precisely does ImageDisk say when it tries to analyze and read the disk?

              I'll take a screenshot tonight.

              >Ideally I'd dump the problematic disk in the problematic drive with a Kryoflux/SCP, which should reveal what is really going on on the disk surface.

              >It is possible to write back a 250kbps IMD disk read in at 300kbps using the "translation" setting. But that does get annoying.
              >The included IMDU tool is supposed to be able to alter this setting in an IMD file, but I seem to recall having problems with that the last time I tried it.

              Interesting, I can look at that.

              >In practice, 10 sectors of 512 bytes per track is a little crowded on each track, so speed issues are a little more likely to affect it.
              >I would at least check the drives both on the PC and the Kaypro to see what the RPM rate currently is.

              On the Kaypro it is right at 300. I can't recall if I checked the PC.

              >Of course, there could be a number of other odd issues at play here. If you have not already done so, try different disks, and clean all the drive heads.

              Heads were cleaned a few weeks ago.

              >I think what you are trying to do really SHOULD work as-is.

              I would think so too; it can write them.

              Comment


                #8
                Here's the bottom line:

                A PC disk controller is blind for a certain period (usually about 500 µsec) after the trailing edge of the index pulse. (Older non-A 8272/765 controllers are blind for 1 millisecond). On standard (IBM System 3) format disks, this is the time that the index address mark (IDAM) passes under the head, so it isn't a problem. However, systems using the Western Digital WD17xx and 27xx FDCs don't demand that the IDAM be included in the format and most vendors left it out, giving a bit more leeway to improve the inter-sector gap spacing.

                Since the width of the index pulse varies from drive manufacturer to manufacturer, different drives will give different results. The certain indicator of this issue is that the PC doesn't see the first sector on the track.

                In the old days, one of the dodges was to simply block the index mark at the drive interface (a bit of tape over the edge connector pin works). Of course, formatting, which depends on the index pulse, won't work, but reading should work. Before cheap microcontrollers, I used my own lashup on a PC ISA card using a WD1772 FDC.

                This almost always is the case with 10-sector x 512 byte formats from WD FDC systems.

                I've posted on this in years past. Obviously, collective memory is short.

                Comment


                  #9
                  This is a 5170 with the standard controller. It will read using the 1.2M drive however.

                  Comment


                    #10
                    Read my post again--drives differ in how they report the index pulse. I'm guessing that you can format, write and read PC-format 360K disks in the 360K drive all day.

                    As I said, if the symptom is that the first sector of a 10/512 disk can't be read in the 360K drive, you now know why.

                    Comment


                      #11
                      Maybe I misunderstood, I thought you were saying it was a limitation of the controller, but why then would it work with a 1.2M drive? Wouldn't the same limitation be a problem?

                      Comment


                        #12
                        I was able to read it in the 1.2M, then use IMDU to translate it to 250kHz, then write it and have it work fine. Still won't read it though in the 360K drive, it just says 0 sectors and gives up now instead of the errors I was getting, but I didn't turn analysis on.

                        Comment


                          #13
                          Okay, I'm barking up the wrong tree. Are you trying to read the copy that you wrote in the 1.2M drive--or the original disk? Unless you started with degaussed disks, reading a disk written in a 1.2M drive using a 48 tpi drive will be, at best, problematical. The problem is that the 360K drive head sees a track that's twice as wide as the one that the 1.2M drive writes. A degaussed disk removes any traces of data previously written.

                          Comment


                            #14
                            I know about the head width issue so never write 40 track disks on an 80 track drive.

                            I'd prefer to read a DSDD disk in the 360K drive, but it won't. It will however read it in the 1.2M drive, but at 300kHz. My goal would have been to archive disks from a 360K drive with the correct setting of 250kHz, but since it can't I suppose I can just use the imdu translate command to translate it after reading it in the 1.2M drive.

                            Comment


                              #15
                              Can the 360K drive (using DOS commands) format and write a plain old DOS 360K disk successfully? Can that disk be read successfully in the 1.2M drive?

                              Comment

                              Working...
                              X