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#103915 - 01/29/16 09:12 AM Re: Making an image of a floppy disk - best way? [Re: Robbbert]  
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rfka01 Offline
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As I understand it, the easiest way to check if a floppy disk is hard sectored, is to check if there are more than one holes on the inner track that passes under the round "window" near the center of the disk. A soft sectored floppy only has one index hole, the hard sectored one has one for every sector.


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#103916 - 01/29/16 09:36 AM Re: Making an image of a floppy disk - best way? [Re: Robbbert]  
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Edstrom Offline
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Yes there are multiple index holes, I just checked. I played with the options in SCP called Index Sensor->Ignore and I got data out of the disk. When set to Requried the disk sounds like a machine gun which I assumed was bad.

However, after reading some articles as the one linked perviously, I assume the problem is the 300 rpm vs 360 rpm and also 48 tpi vs 96 tpi. I need to figure that out to be able to read this disk I guess.

#103917 - 01/29/16 09:45 AM Re: Making an image of a floppy disk - best way? [Re: Robbbert]  
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rfka01 Offline
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I'd contact Herb Johnson, either through the MESS forum or through his S100 website, I think there were controllers for the S100 systems that used hard sectored floppies - he'd probably know about a safe way to image the floppy disk.


NCR DMV- DEC Rainbow- Siemens PCD- ITT 3030-Oly People- Acorn A5000- Olivetti M20
#103918 - 01/29/16 09:49 AM Re: Making an image of a floppy disk - best way? [Re: Robbbert]  
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Edstrom Offline
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Good idea, I drop him a mail.

#103934 - 01/29/16 10:34 PM Re: Making an image of a floppy disk - best way? [Re: Edstrom]  
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Al Kossow Offline
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Originally Posted By Edstrom
Unfortunality it is not an original floppy disk, it is a working disk marked "Boot" and "Kass", Kass means Bad in swedish, however there is also a directory listing included
on piece of paper stuck in the envelop showing that it contains a lot of goodies and also the size in sectors so I hope to salvage some of those, especially the Zebra OS.

The file listing lists 1220 sectors which doesn't relate to 8 sectors and 77 tracks format either. 1220 / 8 / 2 is 76 for a double sided version. So what can I do if it is hard sectored?
1220 is the sum of the SCTRS column and the unused count 879.


I can tell by the label that it is a 16 sectored hard-sectored floppy. You are going to have to determine the recording format based on the flux change (and hopefully sector mark) information recorded by the supercard

#103935 - 01/29/16 10:36 PM Re: Making an image of a floppy disk - best way? [Re: rfka01]  
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Al Kossow Offline
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Originally Posted By rfka01
I'd contact Herb Johnson, either through the MESS forum or through his S100 website, I think there were controllers for the S100 systems that used hard sectored floppies - he'd probably know about a safe way to image the floppy disk.


there is no standard for sector formatting of hard-sectored floppies. you're going to have to figure it out by looking at the data to determine the encoding format

#103974 - 02/01/16 06:54 PM Re: Making an image of a floppy disk - best way? [Re: Robbbert]  
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Edstrom Offline
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I had to turn off index hole checking or the floppy drive stuttered like crazy when SCP was trying to dump the data. As I understand the flux readers, they are oversampling the flux at some (unknown?) rate and then try to decode the encoding, FM, MFM only in order to verify checksums etc, but not for storage.

The stored data has the proprietary headers and then the data is the flux samples?! This means that in order to produce something useful for MAME this flux samples needs to be converted into something the disktools in MAME can understand, or make the disktools understand SCP format directly. Am I correct?

Once the disk is converted into the MAME format I only need the boot ROM and the write a driver for the machine, is that a correct assumption?

Now this particular disk might be trashed (or just dirty) as marked at the label so I might not get the right data out from it, but I will try.

In any case, floppy disk formats and the close relationship with physics is fun. smile I just hooked up a reflectance sensor to my oscilloscope and verified that my drive is spinning with 6 Hz eq 360rpm by making it detect a black piece of electrical tape on the floppy motor. Now, I thought I need a 300rpm floppy drive to read this floppy but depending on the flux sample rate I might be able to compensate for the difference?

Thanks for the observations Al, I'll keep figuring out this flux format, so far I have found nothing useful, but I really don't know what I am looking at, data, FM encoded data or flux samples of Fm encoded data, but I'll get there. smile

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