Writing Amiga Disks with PB 180?

[Super TWiT]

Hey, I was wondering if it would be possible to use my powerbook 180 to read and write amiga disks. To my knowledge it supports some sort of variable speed encoding support, to remain backward compatible with older apples. I was thinking about maybe putting linux on it which has support for amiga filesystems since kernel version 1.3. I also have system 7.5 installed. I am not completely sure if this is possible, and was wondering if anyone thought this might work.

[lsmart]

I used to think that this is not possible, but recently I learned that there is a dos program that can read Amiga diskettes even with vanilla PC drives (http://www.harryfisch.de/amiga/Disk2fdi.zip). So as it seems everything is possible. :-)

[tone007]

Unfortunately this DOS program won't work with the original poster's Mac laptop.

Handy looking tool for everyone else, though.

[Super TWiT]

My powerbook isn't my main computer by the way, I am using a newer computer than that. I just wanted a way to write amiga disks and thought I may have some use for my old powerbook. It may not be well suited to this process. The powerbook 180 is black and white and came out in 1991 BTW

[Matt_H]

It might be possible... but no one's figured out how yet!

[Super TWiT]

I might try this, but I see a problem with one particular step. I don't have any amiga disks, so  I have been putting tape over the hole of my high density disks. Is there anyway I could create disks the amiga could read/boot from within linux?

[lsmart]

Ah, Google is your friend: "Linux supports AFFS hard-drive partitions only. Floppy access is not supported due to incompatibilities between Amiga floppy controllers and PC and workstation controllers." Source: http://www.educ.umu.se/~bjorn/linux/linux-faq/Linux-FAQ-3.html

That being said, try

mkfs -t affs /dev/fd0

(If I recall correctly)

[ncafferkey]

Yes, that would make an FFS floppy, but with PC-type (MFM?) low-level encoding rather than Amiga-type. This is the floppy format that AROS uses BTW.

[Matt_H]

Yes, that would make an FFS floppy, but with PC-type (MFM?) low-level encoding rather than Amiga-type. This is the floppy format that AROS uses BTW.

I think OS4 on AmigaOne uses this, too. Or something similar.

[lsmart]

Yes, that would make an FFS floppy, but with PC-type (MFM?) low-level encoding rather than Amiga-type. This is the floppy format that AROS uses BTW.

Oh, right! That seems plausible.
Do you know more about this? Is it that /dev/fd0 wouldn´t even let you do 11 sectors? Is the sector-label a problem?

Then I guess the software that is reading Amiga-disks under DOS is reading them as if they were MFM and tries to make sense of the corrupted data it gets. Possibly doing multiple scans and applying heuristcs to make up for the data it won´t get. This method is of course not suited for writing.

But with the original posters Powerbook, things might be slightly different. How does the drive read disks? Is it all in the PBs firmware, or does Linux use a special Kernel module to make up for the differences to common PC-hardware?

[Super TWiT]

The Powerbook 180 had an apple supperdrive as the floppy drive. These drives were backwards compatible with the older style macintosh variable speed drives. Other than that I don't know much about it. I don't think it is possible under linux to write an affs filesystem type anyway. Mkfs won't do affs so I think this project is a no go. Also, I can't seem to get linux to go on the powerbook 180. I've never done linux on the 68k. Too bad there wasn't a system 7 application that would do this.

[SamuraiCrow]

Having variable interleave due to drive speed won't help unless your floppy drive controller can generate a track with 11 sectors and only ONE with sync information.  Most floppy controllers generate sync information to every sector thus cutting down the information density stored on the disk.

[mongo]

Then I guess the software that is reading Amiga-disks under DOS is reading them as if they were MFM and tries to make sense of the corrupted data it gets. Possibly doing multiple scans and applying heuristcs to make up for the data it won´t get. This method is of course not suited for writing.

Amiga disks are MFM.