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

  1. #11

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    Quote Originally Posted by Bmurching View Post
    Meaning the controller supports both encoding schemes?
    Yes...
    PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

  2. #12
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    Most of MFM controllers have 10MHz of 20MHz quartz/oscillator while RLL controllers have 15MHz or 30MHz ones.

  3. #13

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    Quote Originally Posted by alecv View Post
    Most of MFM controllers have 10MHz of 20MHz quartz/oscillator while RLL controllers have 15MHz or 30MHz ones.
    Is this to suggest that controllers can or cannot support both encoding schemes?

  4. #14
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    No, cheap controllers did not support both encoding schemes. But there was a "translating" controllers which translated real RLL C/H/S
    into "pseudo MFM" C/H/S with 17 sectors per track.

    JFYI: Intersting reading
    http://bitsavers.trailing-edge.com/c...nual_Jan86.pdf

  5. #15

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    Progress! I received a WD1002A-WX1 controller. After some work, the controller seems to work with my existing ST-225 that was formatted with an Everex EV-391.. I can see the logical drive and read/write without issue. When I connect the ST-4096 the computer throws a 1701 error and Spinrite does not see the disk. The connectors look the same and I have connected the drive identically. I’ve been running through jumper options though the ASCII manual I found is not terribly clear on meaning & location.

    I am noticing that when running Spinrite against the st225 as a sanity check of the controller, Spinrite goes into an endless loop during drive fingerprinting, specifically the “drive write caches” step. I suppose I cannot rule out a controller issue until I do a successful Spinrite run.

  6. #16

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    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 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

  7. #17
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    Check the drive select jumper on the 4096. That may be the issue.

  8. #18

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    Quote 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.

  9. #19

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    Quote 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...

  10. #20

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    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.

    Attachment 60810

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

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