Reading old 3.5 CP/M diskettes using an actual USB floppy drive?

Would that be possible? Or are USB floppy drives fixed to 1.44MB MS-DOS or MAC formats?

The other way: Any compatibility of the USB floppies to some sort of a upd765 or 37C65 floppy controller?

Have to read old, CP/M formatted 3.5" floppies with actual hardware... Have to write software, of course, but will hardware allow to be initialized for some of the proprietary CP/M floppy formats?

Juergen

Reply to
Juergen Marquardt
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Pass on the USB standards.

ANADISK amongst other things is what you need. I did something similar to this about a year ago and I can tell you that most modern drives/PCs (regardless of O/S) will have trouble reading CP/M disks.

There's both the hard sector, and soft sectoring, to consider. CP/M sector layouts are a nightmare. In the end I was writing the alphabet to the disks on the CP/M machine, and then extracting the sectors on a PC, printing it out, and piecing it together sector by sector.

Mine went something like 1,12,2,13,3,14,4,15,5,16 etc.

comp.os.cpm may be worth a look in. They have experience of this.

And what makes it EVEN MORE FUN!! is that different builds of CP/M lay down the sectors in completely different ways. :-)

First off, get yourself an old IBM laptop, say a 80486 Thinkpad 755C. That was the most reliable machine I had. The modern PC's *could* address the sectors yet read garbled data.

Who on earth has given you this task anyway? :-)

Reply to
Aly

I've been able to read/write non-standard format floppies using a USB floppy drive. However, it's not possbile to use a USB drive to format floppies to non-standard format under Linux.

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Grant Edwards
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Back in the olden days this was called sector interleaving, and as best I remember, used only on soft sectored disc drives. It was a technique to synchronize "high speed" hardware (instructions often took many microseconds to execute) with those slowly revolving mechanical discs. Most machines were optimized to have the interleave factor set to make the hardware read/write the disk in as few rotations per track as possible. Some could only do one sector per revolution, others 2 or more. The disk controllers of the period usually required programming on a sector by sector basis. Ah, the good old days.

Regardless of the interleave factor, the disks were compatible from machine to machine (presuming both machines had the same density, number of sides, etc.) because the sector number was contained in the sector header. Performance might vary widely because of differing interleave factors, but the data would be read/written in the correct sectors.

Thanks for the memories Scott

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Not Really Me

Oh, yes. I now remember that we spent hours and hours to tune the interleave factor :-)

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42Bastian Schick

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