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Looking for 8-bit MFM controller for a ST-4096 drive... suggestions?

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    #16
    Could also be format incompatibility, i.e., the Everex format is not completely compatible with the WD controller.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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      #17
      Check the drive select jumper on the 4096. That may be the issue.
      Reach me: vcfblackhole _at_ protonmail dot com.

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        #18
        Originally posted by Stone View Post
        Could also be format incompatibility, i.e., the Everex format is not completely compatible with the WD controller.
        This turned out to be the right answer as to why the ST225 (formatted with the Everex controller) was throwing errors during fingerprinting with Spinrite. I have that second ST225 drive (has some errors but a good test article) and I did a fresh format using the controller ROM via debug, and Spinrite was happy doing its thorough analysis thereafter. (The only other difference I'd mention is that I downgraded my boot OS from DOS 6.22 to 5.0 though I imagine that would't have much of an impact. Unrelated to the ST4096 but I noticed that with the ST225, switching from the Everex controller to the WD, the system now recommends a 4:1 interleave (vs 5:1 with the Everex controller). I found myself smiling and thinking, "ah, is MFM controller performance another variable I need to study?!"

        Once Spinrite is complete on the ST225 (both copies I have) I'll take a closer look at jumpers on the ST4096.

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          #19
          Originally posted by Chuck(G) View Post
          Check the drive select jumper on the 4096. That may be the issue.
          Checked, I think I have it correct. It's interesting how the ST225 has so few jumpers whereas the ST4096 has so many, many, many different jumper blocks...

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            #20
            Continuing to work this...

            I realized the wd1002a ROM was not the 62-000094-xxx version recommended so I managed to get another controller with the right BIOS. this drive’s debug LLF seems to work. I did a full check using the ST-225 and get no errors or issues. When I try debug low level format of the ST4096, configuring the drive dynamically and I think properly (1024 9 1025 1025 11 5) I get an Error 80. The only thing I’ve found thus far is that Error 80 may mean insufficient power. This is a 35 year old PSU powering a fairly beastly drive, so perhaps. I am going to see if I can power the drive alone off a separate PSU. While I prep to do so, I wanted to check in if anyone else has suggestions.

            I disassembled and cleaned the PCB, connectors etc and even found a beer cap wedged between the board and drive (did someone use this as an opener?) but I have not yet designed to open up the drive itself to look for a stuck actuator or some such. The platters definitely spin and I can hear some thunks suggesting the heads move, but it’s hard to say with the cover on.



            The controller as currently configured.
            Last edited by Bmurching; May 9, 2020, 05:50 PM.

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              #21
              Error 80 is a Time Out/Not Ready Error.

              It is fairly meaningless error and can mean a number of different things.

              If the drive is spinning, and sounds like the head is moving:
              - The larger control cable is connected incorrectly
              - The larger control cable is STILL connected incorrectly :P
              - The larger control cable is damaged
              - The drive select jumper is set wrong
              - The controller does not detect a "ready" state on the Ready pin
              - The controller does not detect an index pulse on the Index pin
              - The controller does not detect that the head has reached track zero using the Track Zero pin.
              - The drive logic board is damaged (likely if you found a bottlecap stuck in it)
              - The controller is damaged (you already ruled this out)

              You can actually check the ready state with a logic probe and manually activating the drive select line. When powered on, it should be "not ready" until it spins up and the head seeks track zero, then it becomes "ready", and indicates that part of the drive should be working OK. (You can also check index, but if that were not working, it should also fail to enter the ready state).

              Some of these issues could be caused by power issues. Worth checking, but if it spins up, that seem a little unlikely.

              I'd avoid opening it until exhausting all other options.

              Note that a head crash or damaged platter will still allow a controller to attempt to format.

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                #22
                I've found that many of these MFM drives will format perfectly (or so it appears) right up to the end of the process. The only problem is that they actually didn't (format) and they don't work or respond to anything. It's just the nature of the beast.
                PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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                  #23
                  Originally posted by SomeGuy View Post
                  Error 80 is a Time Out/Not Ready Error.

                  It is fairly meaningless error and can mean a number of different things.

                  You can actually check the ready state with a logic probe and manually activating the drive select line. When powered on, it should be "not ready" until it spins up and the head seeks track zero, then it becomes "ready", and indicates that part of the drive should be working OK. (You can also check index, but if that were not working, it should also fail to enter the ready state).
                  I'm not too conversant with a logic probe... which is to say I've never used one. So, it took a while to learn about it, find and purchase one (Elenco LP-560) and learn to use it! It's a handy device though there remains much to learn.

                  For the ST4096, what I've noticed are the drive select 1 and index lines going high when the machine is powered up; about 20 seconds into POST, both DS1 and IDX start pulsing for about 10 -15 seconds... by 'pulsing' the logic probe shows rapidly flashing high/low indicators and the speaker chime is a somewhat noisy, slightly irregular alternating tone. After this, both lines go high again. Sometime during this pulsing the computer throws a 1701 error. I was measuring from the pins on the back of the controller; I'm fairly certain I'm checking the right pins. In contrast with the working ST225, both the above lines go high on power up and stay high all the way through HD boot. So, the good news is that the logic probe is helping me capture a behavior difference in signals on the control connector between the working and problematic drive.

                  In contrast, the ready line goes high on both drives immediately after power up, and stays there all the way through POST.

                  Another interesting observation: pin 16 on the control connector is supposed to be reserved and was indeed unconnected (no LED/tone) with the ST225, but it runs high with the ST4096.

                  My probe was connected to ground (the chassis) and +5VDC from one of the motherboard speaker connector pins... hope that's correct, as it's the first time I did this.

                  Since DS2/3/4 lines are open with both drives, I believe the drive select jumper is correct. I am also certain the cables, controller and cable connections are OK, so the issue must be with the drive or with the controller's suitability for this drive.

                  Next steps I'm considering:
                  - I believe the ST4096 has 16 heads and needs a controller supporting 16heads. I noticed pin 2 on the control line (head sel 3) was low for both the ST4096 and ST225 drives, whereas the other three head select pins were high on both drives. This makes me wonder whether my controller is 16-head friendly?
                  - The aforementioned pin 16 behavior difference also is interesting
                  - I have an oscilloscope and will try to better capture the signal behavior of the index and DS1 lines

                  I'll take any and all suggestions on other areas to explore.
                  Last edited by Bmurching; May 16, 2020, 03:02 PM.

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                    #24
                    ST4096 has 9 heads.
                    --
                    Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"

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                      #25
                      I remember fiddling with an ST4096 on an 8-bit controller (which didn't support 9 heads) a long time ago, just to test the drive. I think I had to tape off some pin on the drive connector to make it work (with only 8 heads used). But I can't remember what pin that was and where I got that info.

                      The drive definitely didn't work without this modification on a standard controller which only supports 8 heads. Some controllers can also be jumpered to support 9 heads.

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                        #26
                        Interesting, had not thought about that. Glancing at the pinouts, perhaps try covering Pin 2 on the control cable. (Reduced Write / fourth head select).

                        If a non-existent head were inadvertently selected, that could cause the drive to appear not ready and time out.

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