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CF card format to FAT12

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First post, by fool

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I have DOS 3.21 in XT-clone (Commodore PC 10). Build one XTIDE-lite to ease file transfers. Original 360kB floppy drivers are not very handy for that...
OK then, DOS 3.21 FAT12 supports single max 32MB partition. I can make about 20MB partition on CF card with fdisk and that works fine on Commodore. I cannot see that specific partition using the drive on my main computer via USB reader - it's just normal 256MB drive in Windows. I can copy files in it, but obviously cannot see them in the other system.

Yet I haven't found Windows/Linux tool to format it <32MB FAT12.
1. mkfsdos.exe can format it to FAT12, but it's still 256MB. It won't accept smaller than 128 sectors-per-cluster.
2. Windows partition tool won't do a thing...
3. Windows 10 diskpart can create small 32MB parition but it doesn't understand format to FAT12.

Any ideas? And I don't want to upgrade DOS... 😀

I'll try diskpart on Windows XP some day, heard some rumors FAT12 is supported.

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Reply 1 of 2, by lolo799

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Make a complete dump of your CF card (after having it properly partitioned and formatted on your XT clone) using hdd raw copy tool, win32diskimager, dd or any software that does a full dump, then open your new 256MB image with Winimage, it should let you access the partition.

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Reply 2 of 2, by Jo22

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fool wrote on 2021-12-30, 15:48:

Any ideas? And I don't want to upgrade DOS... 😀

Oi, that's tricky then.. I'm using MS-DOS 6.2x on my XT clone because of all those limitations.
That being said, I understand your desire. If feasible, I'd rather use a DOS version from the mid-80s, too.

What about PC-DOS 3.30? It still has 32MB partition limit, but supports the old fashioned FAT16, at least (we nowadays use FAT16B).

Or how about Compaq DOS 3.x?
The latest release supported partitions bigger than 32MB..

I'm sorry, that's all that comes to mind right now.
If you're adventurous, you could try out filesystem drivers in TSR format.
Not sure if they work for on DOS 3.2, though.
They would provide a faux "network drive" through a drive letter.

Anyway, I didn't mean to annoy you.
These are just my two cents. 🙂

Edit: Lolo799 has a goid idea here. You could use that dump for experiments, too.
PCem/86Box can read raw images.
You could set up several profiles (DOS, Win98, XP) and experiment with them.
Once you've been successful, you could write the dump back to your physical CF abd see what happens.

Edit: Correction, plain FAT16 support started with DOS 3 already.
Here's a chart that shows supported partition sizes in DOS.
MS-DOS 3.31 can do FAT16B and 512MB partitions.
That seems to be that "Compaq DOS"..

https://en.m.wikipedia.org/wiki/Comparison_of … erating_systems

https://www.pcjs.org/software/pcx86/sys/dos/compaq/3.31/

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