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Ohio Scientific C1PMF Disk Drive


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I found an Ohio Scientific disk drive with a Model of C1PMF in my garage that I forgot I even had.  I can't seem to find anything about it on the internet.  I don't believe the I have the C1P computer itself, (I think I would have remembered that.) so I have no way to test if it is still functional.  I did clean it up and I opened it up to see what is inside.  It has just the floppy disk drive and a power supply.  I tested the power supply and found that the 5V and 12V are still good.  I thought for sure the drive would have a bad drive belt but it seems to have a direct drive motor.  It is a double sided 5 1/4 inch, half height drive.  I was able to find some information on the drive itself, which is a Mitsubishi M4853.  It's a little unusual as it is double sided, double density, but it has 80 tracks.  There are only 16 sectors per track so total formatted capacity is 640K.   Does anybody know if these were standard drives for the Challenger C1P?

 

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I cannot help with any information about the drive, but I am fascinated/amused by the idea of finding previously unknown vintage hardware in your own garage! 

 

It makes me want to revisit my storage unit; perhaps someone has added something interesting since my last visit. It has been a few years. 

 

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  • 2 weeks later...

Until this thread I never knew there really was such thing as an 80-track "double density" or "quad density" 5.25" drive.

 

I even found a manual for the Mitsubishi M4853 already on archive.org: https://archive.org/details/bitsavers_mitsubishi52M4853Specifications_1633993

 

It's interesting the specs indicate only 636KB max capacity... You would think that it should be capable of 360K X 2. Maybe it's just a holdover of old DOS versions before they realized they could put 18 256 byte sectors per track. vs 16 in the specs.

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On 10/13/2019 at 9:26 PM, mutterminder said:

I found an Ohio Scientific disk drive with a Model of C1PMF in my garage that I forgot I even had.  I can't seem to find anything about it on the internet.  I don't believe the I have the C1P computer itself, (I think I would have remembered that.) so I have no way to test if it is still functional.  I did clean it up and I opened it up to see what is inside.  It has just the floppy disk drive and a power supply.  I tested the power supply and found that the 5V and 12V are still good.  I thought for sure the drive would have a bad drive belt but it seems to have a direct drive motor.  It is a double sided 5 1/4 inch, half height drive.  I was able to find some information on the drive itself, which is a Mitsubishi M4853.  It's a little unusual as it is double sided, double density, but it has 80 tracks.  There are only 16 sectors per track so total formatted capacity is 640K.   Does anybody know if these were standard drives for the Challenger C1P?

 

80-track drives are pretty standard.  The IBM PC, and most of the home-computer crowd skipped this type, but they were common enough in industry.  They have exactly the same specs for storage as a 720k 3.5" floppy drive, which latter were super-common in later PC days.  Why it lists 635k as the storage is odd, but it is still a 720k drive.  Disk formats were wildly disparate in those days.  If you hang it off of a Percom or ATR8000 controller, you will be able to test it.  The ideal tester would be The Black Box Floppy Board, or an old IBM PC-compatible that has a real floppy card in it.

 

Best,

 

Jeff

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  • 1 month later...

Well actually I do have and ATR8000 as well.   I suspect that it might be good as it looks to be in pretty good shape, but it is more than 30 years old so you never know.  I was just curious if anybody knows if these were commonly used with the Ohio Scientific?  Since some of their computers were actually using 8" drives, I guess it's not too outrageous to think they could have used this drive.  I wonder if I could use it with a CoCo?....

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5 hours ago, mutterminder said:

Well actually I do have and ATR8000 as well.   I suspect that it might be good as it looks to be in pretty good shape, but it is more than 30 years old so you never know.  I was just curious if anybody knows if these were commonly used with the Ohio Scientific?  Since some of their computers were actually using 8" drives, I guess it's not too outrageous to think they could have used this drive.  I wonder if I could use it with a CoCo?....

I'd be surprised if you couldn't.  One of the many things that made the COCO such an enviable machine is the floppy interface.  Your's costs more to get a drive going, but once done, you have high-speed storage.  The Atari and Commodore needed significantly more to get high-speed io.  I really envied OS9 on the coco3 back in those days.  Pound for pound, the COCO can stand its ground with any 8-bit and better most.  Anawho, there's surely an interface for your coco that will run a standard drive.  The ATR will do it too, as will a percom controller.

 

Best,

 

Jeff

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