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Why did the 5150 come with a tape connector?

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    #46
    There is also a floppy drive without positioning capability; the Mitsumi QuickDisk--used on various items, such as the Famicom games, various bits of MIDI kit and at least one manufacturer's word processor. Once activated, the head traces a spiral track from start to end, and automatically returns to the starting position. Think of it as a endless tape loop on disk.
    Reach me: vcfblackhole _at_ protonmail dot com.

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      #47
      Originally posted by krebizfan View Post
      The Exetron Stringy Floppy and Sinclair Microdrive would disagree. Continuous loop tape formats were used successfully for data storage. Not being able to rewind doesn't matter since the tape will pass the beginning in a few seconds and resume trying to find files.
      Here's a picture of the aforementioned Compucolor and a dual "Floppy Tape" 8-track drive:

      Compucolor8001.jpg
      These drives essentially worked like the Stringy Floppy and friends just, well, 8-track. They used extra-short tapes so each track would loop around in only couple minutes or so at high speed; at 4800 baud with 8 tracks you need only a few minutes worth of track to hold about a total of 1MB of storage.

      (The system specified that it could do 1MB of storage per tape, so here's the rough math on that: 1MB is a bit north of 8 million bits and we have 8 tracks, so we need to hold 128K, or a million bits per track. At 4800 baud storing a million bits takes a little over three and a half minutes of tape. Maybe we should pad that out to five minutes to allow for formatting and file system markers.)

      Therefore assuming the system was smart enough to use some kind of directory system at the start of the tape loops (8-tracks use a conductive marker to signal audio players to switch to the next track, in a digital system that would be your index mark) it shouldn't take more than a few minutes to locate and load a piece of information anywhere on the tape even if the "scanning" speed is just a small multiple of the normal play speed. "A few minutes" isn't great but at least it's automatic compared to a plain linear cassette deck.

      Not that such a system was ever likely to work well in practice. 8-track was designed to be rugged and forgiving in applications like car music players, what it didn't offer was precision or high-fidelity. Unless you used special high-strength tape, which I guess could be an option with such a short loop, I doubt you could up the scanning speed much over over 2X, and track alignment/bleed-through was probably also a problem. No surprise these didn't catch on since floppy drives already existed and weren't *that* much more expensive in the grand scheme of things. (Making something like a "floppy tape" actually reliable would probably result in a tape mechanism at least as expensive.)

      Let's not forget that non-continuous loop versions of automatic tape drives based on audio decks also existed:

      adam.jpg
      And likewise were pretty much a terrible idea in retrospect.
      My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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        #48
        It is unfair to point to the Coleco Adam for tape drive failure. The power on degausser of the Adam would have destroyed any internal magnetic storage media, be it the originally planned Stringy Floppy, the actually used DDP, or the prototyped Tabor 3.25" floppy drives.

        High speed cassette mechanisms could be made to work like the DEC TU-60. The continuous loop tapes needed time to thoroughly debug. Sinclair was selling microdrives for about 5 years before they let outsiders with knowledge of how tape works improve the design. It appears that those who stuck with it until the last revisions got a surprisingly reliable storage system that still works if the cartridges get a new piece of felt. Not what one would have expected based on the initially released models.

        A lot of the tape failures like Digital Group Phi-Deck or the Floppy Tape have to do with a poor understanding of interference. The companies that added shielding were able to get the disk drive in place with few problems.

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          #49
          Originally posted by Chuck(G) View Post
          There is also a floppy drive without positioning capability; the Mitsumi QuickDisk--used on various items, such as the Famicom games, various bits of MIDI kit and at least one manufacturer's word processor. Once activated, the head traces a spiral track from start to end, and automatically returns to the starting position. Think of it as a endless tape loop on disk.
          I'll be, never knew the FDS worked that way. Seems like it would be massively inefficient in utilizing the disk surface

          Comment


            #50
            There were numerous decks that used audio-type cassette tape in digital mode. Initially, they were used as substitutes for paper tape reader/punches. I owned and used one such early on, a nice Techtran dual-cassette model. It had high-speed search, could make offline copies and supported data rates up to 9600 bps. NCR also used the cassette storage format, as did MFE and you occasionally can find PLCs (e.g. Mitsubishi) with cassette drives. All not audio, but digital.

            Also used with embroidery equipment, etc. Eventually, there were floppy drive units made to emulate the tape units.
            Reach me: vcfblackhole _at_ protonmail dot com.

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              #51
              Originally posted by krebizfan View Post
              A lot of the tape failures like Digital Group Phi-Deck or the Floppy Tape have to do with a poor understanding of interference. The companies that added shielding were able to get the disk drive in place with few problems.
              I know these systems *can* work well; the Exatron Stringy Floppy had a pretty good reputation so far as I recall reading. (I never owned one, though.) One thing the Exatron device had going for it though was it was mechanically extremely simple, basically just a lump of metal with a motor, and the motor its only moving part. Among other things a standard 8-Track based audio deck uses a crude solenoid/ratchet system for flinging the drive head bodily between tracks. Alignment issues caused by this unstable element were a common issue for audio playing, and this would be magnified in a computer application.

              Not that you couldn't make this more reliable by using some more precise mechanism with higher tolerances, but that's the point I was making about cost. Something as simple as the Exatron or Sinclair Microdrive was definitely cheaper and simpler than a floppy drive, but I would question whether that would be true for a "data grade" 8-track deck.

              And, yeah, I'll grant there were cassette based systems that worked better than the Adam's. I just suffered the misfortune of actually having one of those when I was a kid so, yeah, damage.
              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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