On Friday 07 June 2013 14:40:21 Patrick Serru did opine:

Le vendredi 07 juin 2013, Gene Heskett a أ©crit :

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On Friday 07 June 2013 09:04:36 Martin Gregorie did opine:

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Some time back my 68000-based OS/9 system died and I needed to get stuff off the 3.5" floppies I use to back it up.

I'm a Linux user, so I used setfdprm to fiddle with the parameters in the 'floppy' driver and was able to image the disks successfully and then use the os9exec OS/9 emulator to access their contents.

The reason I'm mentioning this is that I used a standard Linux driver, which normally uses 512b blocks and a standard 3.5" drive to read OS/9 floppies while the parameters needed to read the OS/9 floppies were:

hd sect=34 ssize=256 head=2 cyl=80 tracksize=8704 dtr=0 zerobased

I haven't yet tried it on any Flex-09 disks: mine all use single density for track zero and deduce the format of the other tracks from its contents. I wrote the drivers and may have diddled with the formatter when I replaced the original two disk FD card with a Windrush card that that handles 4 drives off a pair of FDC chips.

I'm posting this to say thanks for writing such a good "get out of jail free" utility and as an indication to any other Linux users of just what setfdprm is capable of.

Martin

I don't want to rain on this parade, but there are FDC's on some motherboards that flat will not access disks other than 512 byte/sector.

The board in this box is one such. Doing a setfdparm to the 256 byte format that the 6809 os9 machines use, and then sending dd to either read or write a disk image will churn and hammer the drive for several retry cycles, then apparently tosses the dice to see if it locks this quad core phenom up, requiring a hardware reset or returns an error. If a write was attempted, I can take the disk to a real os9 system and inspect it with dEd, and it has not been touched. This is an ASUS M2N-SLI Deluxe board I paid nearly 300 USD for, not too long after the phenoms came out.

The moral I guess is that if you need to access 256 byte per sector disks, make sure the FDC on the board you are buying will indeed work before dropping the card for it.

Cheers, Gene

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  Hi Gene,

  It worked â€‌well enougthâ€‌ for me. I used such commands:

fdrawcmd drive=/dev/fd0 readid 0 rate=0 need_seek track=0 espectigng a restore command, and for most of the work: fdrawcmd read 0 0 0 3 1 52 0x1b 0xff length=256 Could it be working because of the length parameter, the 256 remaining bytes being silently ignored?

  I tryed first to read full track by full track (26 sectors x 256

bytes each, two sides by cylinder), but unsuccessfully. That's why I thought to such a "256 remaining bytes being silently ignored" reason.

  I wrote â€‌well enougthâ€‌ because I have problems with 3 or 4 of

the 16 disks. A side, allways the same, seems to randomly miss sectors. I wonder if a head of the driver would not be durty or near its end of life. Could it be a Media problem, that would result in too low level signals? I configured the drive, in the BIOS, as a 1.2M, 5.25" floppy: could matter? The medias are marked "double sided, high density, 96 TPI/1.6 M.B. Sect: soft". Who could tell me how many types of media (the magnetic coating point of view) existed for the 5.25" floppy (but the "soft" sector case, then).

  Cheers,

Patrick

Excuse, pleas my poor english writing.

I think I'm understanding you.

First off, for the older disk formats, the 1.2 or 1.6 meg 5.25" format is a non starter because the head is not moving a full track, only a half track as its stepping inward. We do 'double step' those however.

Second, the vast majority of those old disks were recorded at baud rates in the 125/250 kilobaud range, and many of the newer drives simply cannot reliably read the data that slowly.

So I would dismount the drive, give its head motion rails a good clean and lube (vaselene works well for the lube in most cases, and lasts longer than the other light oils extant), and make sure the drive screws thread isn't full of old, dried & caked up grease, destroying the accuracy of the head positioning my making the single wire in the groove that most newer drives use for a drive nut, up out of the groove, riding the hardened grease rather than the nice shiny metal.

Take a Q-tip, wet with paint thinner alcohol, and wipe between the heads gently.

Write down the drives brand and model number so you can look it up on the net. You'll want to know just what sort of a beast you have.

The 1.2 meg drives also spin at 360 rpms, (duplicating the old 8" drives) where most spin the disk at 300 revs, there should be a software switch to set that but some of the earlier drives were flea clip programmed on the drives circuit board. The data baud rate is also 1 megabaud. The 1.6 meg drives spin 300 rpms, and that 1 megabaud then gives 1.6 megs per disk Some of the newer 2.88 3.5" drives (they make good target practice for your deer rifle) have heads that can function with a 2 megabaud FDC chip, but that wasn't very dependable, and should be considered the floppy disks last gasp for air before going down for the 3rd time.

Now, carve this in granite: If that drive is in fact a 96 tpi drive, the ONLY way you can write a 48 tpi disk in it is if the disk has been wiped clean by a bulk disk or tape eraser. Disks marked HD or QD probably can't be wiped well enough because the erasers you can buy today are too puny.

You can read a 48 tpi disk if setfdparm was used correctly, but you can't write to it unless that is the only drive it will ever be read in again. The problem when writing is that the 96 tpi head doesn't write a wide enough track to over write older, wider tracked 48 tpi information, so the 48 tpi head in the target machine reads a mixture of old & new data, gets all confused and give you garbage if not all sorts of read errors.

Generally, I don't do floppies anymore as we now have a wired connection at 115 kilobaud to my particular 'legacy' computer.

HD and QD rated disks are pretty hard magnetically so writes are often weak and the data fades, sometimes before you can read it back. So stick with 'DD' disks if you can, which can be used in 300 rpm, 250 kilobaud 96 tpi drives for a capacity of 720k with long term reliability. They also work well in 360k formats.

Somewhere in this soap box session might be something you can use, I hope so. :)

Cheers, Gene