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Thread: HD on 3.5" DD floppies--DON'T DO IT!

  1. #11
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    Any thoughts as to why IBM used host-determined density, when the drive and media clearly had density detection/reporting built in? I mean, a novice DOS user types FORMAT A: and they get a 1.44mb format (with several errors) on DSDD media with otherwise no warning -- didn't anyone think that would be a problem?
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  2. #12
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    You have me there--my first HD drive was a Sony; it detected the density hole. Could it be that the PS/2 used IBM-spec-ed (Alps) drives and someone forgot about the media-type sensing? Or it could have been that someone at IBM believed that the 3.5" HD drives were supposed to follow the convention set by the 5.25" HD drives--that using the correct media was the responsibility of the user.

    Might make for an interesting story from someone who was there.

  3. #13
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    Quote Originally Posted by Trixter View Post
    Any thoughts as to why IBM used host-determined density, when the drive and media clearly had density detection/reporting built in? I mean, a novice DOS user types FORMAT A: and they get a 1.44mb format (with several errors) on DSDD media with otherwise no warning -- didn't anyone think that would be a problem?
    From what I remember some of the earliest PS/2 Model's 3.5" drives (PS/2 Model 50s and Model 60s) didn't sport the media detect sensor. In fact we have the reverse problem, having enough 720KB media for some of the older, archived "Option" diskettes, which were distiributed on 720KB diskette, and packaged as Sydex diskette re-creating EXEs on the IBM PCCBBS.

  4. #14
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    Quote Originally Posted by WBST View Post
    From what I remember some of the earliest PS/2 Model's 3.5" drives (PS/2 Model 50s and Model 60s) didn't sport the media detect sensor.
    I don't think any of the "first gen" PS/2s (50-80, and at least through the 55sx, which I know came a little later) had the media detect sensor. Maybe they finally gave in on some of the later ones.
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  5. #15
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    Quote Originally Posted by WBST View Post
    ... and packaged as Sydex diskette re-creating EXEs on the IBM PCCBBS.
    Ah, I remember that one. It was fun--writing a dual-mode (OS/2 and DOS) self-extractor for the IBM PCC folks.

    It might be possible (should be, actually) to write a self-extractor that produces "raw" images, if that's any help. I don't know if this would run afoul of any IBM copyright claims, however.

  6. #16

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    what about the opposite? writing 9SPT on HD disks? is that likely to hold up?

  7. #17
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    Better than the reverse, I suspect. I've gotten lots of those in from gear that's "HD-blind" and writes DD data from at least 20 years back.

  8. #18
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    Quote Originally Posted by Eudimorphodon View Post
    These days DD floppies are so rare I've resorted to doing the reverse, bulk-erasing HD floppies so I can use them in double-density machines. (Specifically old Apple 3.5" drives.) I've gotten away with it (in the sense the disks will usually work semi-reliably in most of the drives I've tried them in, at least for a while), but the only thing I ever use those disks for is writing OS and program disks that are disposable and trivial to recreate.
    I've done this a lot for my Tandy 1000HX and 1100FD. Everybody's got boxes of old 1.44MB disks laying around, and the older ones from the 90's were almost always of better quality than the end of manufacture floppies from Staples in the early 2000's (you could get several bad disks right out of the box), and the older ones are worth reusing. I usually do a complete format on an HD drive first, to be sure that there aren't any bad sectors. Then tape over the HD hole, reformat them for 720K, put on a new label, and away we go.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, and some random Pentium in a Hewitt Rand chassis...

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