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Looking for a replica of the original CP/M 2.2 8 inch disk

Chuck, I've seen in another thread that you have also shared the images of the original MP/M floppies. Thanks for this !
Having these type of generic operating system floppy disks is very valuable.
 
By the way, the original CP/M was FM disks and used the worst-case data pattern of hex E5 for the blank sector data, and thusly the "erased" directory entry value. Later when machines started using double density, CP/M still had to use E5 even though it was no longer the worst case data formatting pattern. I seem to recall a two-byte pattern that was the MFM worst case. Chuck will know off the top of his head. :)
 
Amardeep-AC9MF said:
By the way, the original CP/M was FM disks and used the worst-case data pattern of hex E5 for the blank sector data, and thusly the "erased" directory entry value. Later when machines started using double density, CP/M still had to use E5 even though it was no longer the worst case data formatting pattern. I seem to recall a two-byte pattern that was the MFM worst case. Chuck will know off the top of his head. :)
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I think the real reason is that initially, not all systems could be assumed to be able to LL-format floppies. Some required pre-formatted ones from the factory.
The 3740 disks out of the box, with the exception of the first track, noted above, were formatted to E5s on all of the unwritten tracks.
 
E5 is EBCDIC for 'V' - the last value written to data sectors after/while Verifying them. If you look at the first track/sectors of a "3740 formatted floppy" you'll see other EBCDIC values and patterns, that are described by IBM to initialize the floppy for use on their equipment. I ran across some documents somewhere about the original IBM equipment to use 8" floppies, and it described what a formatted diskette was like - all defined in EBCDIC values. The first few sectors (part of the CP/M system/boot area) contain structures that hold indexes and directories for the data as defined by IBM. The E5 patterns start on track 1 or 2, I forget which.

Note that 8" floppies were commonly sold pre-formatted for "IBM 3740" equipment. There were no sectors recorded as DDM, or if there were they were in addition to the normal 1-26 sectors on each track, as the floppies could be used on CP/M without reformatting and all sectors on all tracks were available.
 
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I have a question regarding floppy formats for CP/M and derivatives.
I've read ealier that some floppy formats seem to be named, like "A1"

Is there a list of all 'standard' floppy format for CP/M and derivatives ?
Or did each computer manufacturer 'invent' its own CPM floppy format ?

I'm asking this because, I've recently dumped a certain amount of 8" CP/M-80, CP/M-86, CCPM-86 and MPM-86 and I've seen a variety of formats .
For example:
  • single/double sided
  • single, double density (with double density, the system tracks are often still in single density)
  • number of sectors per track : 8, 15, 26
  • sector size 128, 256, 512, 1024 bytes
  • various skew factors
  • starting sector id at 0 or 1
  • sector numbering continuing or not on the second side
  • various 'root directory' size (taking the DOS terminology here, I don't know how to name it for CP/M)
  • block addressing 8 or 16 bits
  • 2 or 4 system tracks
.
 
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There are literally hundreds. Not only that, but encoding/modulation can vary considerably. For example, where would you put the format for Victor 9000?
Even on the hoary old MDS-800, the double-density 8" disks used MMFM... I wrote 22Disk initially with only about 5 formats. Currently, the count stands at about 600.

That this would be news to anyone after 35+ years amazes me.
 
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Some people (like me) are still discovering CP/M nowdays :)

I recently started to develop small tools to explore the 8" CPM floppy images I had created and extract files from them. I have around 5 formats for now, and from what I am reading, I guess there's a long way to go if I want to get an extensive support :unsure: But this is not my goal. Currently, I'm trying to understand better the CP/M technical details and extract useful data for the computers I'm working on (french computers from early 80's).

By the way, the computer history preservation association I'm member of has a MDS-800, unfortunately without the 8" floppy disks. Having the original CP/M 2.2 working on it would be really nice. But without floppy controllers (I guess), it may be very complicated.
 
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gotcha said:
Some people (like me) are still discovering CP/M nowdays :)
...
By the way, the computer history preservation association I'm member ...
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Welcome to the fun world of CP/M and 8bit computing. It is a great testament to CP/M's design elegance, portability and simplicity that new comers and preservation groups are discovering CP/M a new, even after almost 50 years, and find it worth learning. The late Dr. Kildall began developing CP/M in 1973 and the first pre-release 1.2 as custom DOS for Tordoe's S100 FDC in 1975. Yet, here we are in 2024 and hopefully for many more decades, will continue to enjoy CP/M.

Thanks to the many generous experts, the likes of Chuck(G), all whom have been sharing their expertise here. The 70's and 80's documentation might seem terse at times, but such was the nature of the industry in its early days; each day brought new innovation faster than the documentation can fully detail it. Providing for lots of adventurous explorations (and sometimes frustrating "fun") solving the puzzles. Wish you all happy computing.
 
Chuck, I recently picked up a 5.25" Teac floppy drive and it came with a stack of diskettes. There was a Sydex copy of 22Disk included in the stack along with a couple of Sydex utility diskettes.
 
Doesn't surprise me at all. I still get inquiries for the product, even though a system with a legacy floppy drive hasn't been manufactured in well over a decade.
 
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