Is this a IIgs disk? If so, what filesystem is it?

[hjalfi]

I've been given a disk image read with my FluxEngine floppy disk reader. The owner says it came from an Apple II of some description. The disk is in CLV Mac 800kB format (or possibly it's an 800kB disk reformatted as a 400kB disk; there are a lot of bad sectors on the back of the disk). This suggests an Apple IIgs, which is the only 8-bit system which used the Mac format, right?

Except, my understanding of the IIgs is that it used a variation of the ProDOS file system, which I don't think this is. The beginning of the disk contains two blocks of empty boot sector, and then I would expect the volume directory. On this disk, it looks like this:

00000400 42 44 AC FC 43 FD B1 A2 BF 42 03 00 00 0F 00 03 BD..C....B...... 00000410 01 69 06 39 00 00 02 00 00 00 08 00 00 04 00 00 .i.9............ 00000420 00 2B 04 9F 05 42 6C 61 6E 6B 00 00 00 00 00 00 .+...Blank...... 00000430 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000440 00 00 00 00 00 00 00 00 01 98 00 00 18 00 00 00 ................ 00000450 18 00 00 03 00 00 00 0F 00 00 00 03 00 00 00 00 ................ 00000460 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000470 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000480 00 00 00 00 18 00 00 00 00 0C 00 00 00 00 00 00 ................ 00000490 00 00 00 00 30 00 00 0C 00 0C 01 6A 00 0C 00 00 ....0......j....

This disk label is clearly 'Blank', but is a Pascal string starting at 0x424. The ProDOS disk label should start at 0x401. 0x424 is the right address for a MFS file system disk label, but on those the superblock should start with the magic number 0xd2d7, which doesn't match this. (Other things are different too.)

Any ideas what this might be (and where I can find documentation on it)?

Thanks!

 

[nyef]

$4244 is the HFS filesystem signature, try Inside Macintosh volume IV, chapter 19, "File Manager".

 

[Arbee]

BD is HFS format. It could still have been written on a IIgs, but that's somewhat less likely.

 

[hjalfi]

I did try HFS and it didn't work; I'll have another look (it's possible there's something wrong with my HFS driver).

It's there a 400kB HFS variant, or were those disks always MFS?

 

[cheesestraws]

It's there a 400kB HFS variant, or were those disks always MFS?

It wasn't usual, but one could use HFS on 400k discs. One had to hold down keys to do a secret handshake while attempting to initialise the disc.

 

[hjalfi]

All right, I now believe that this is a perfectly normal HFS 800kB disk with track 0 side 1 missing, rendering it unmountable. Therefore, not very interesting! But thanks for the help anyway.

(Incidentally, if anyone knows of any MFS flux-level disk images they can point me at, I'd love to add support for those too...)