Re: Who knows about the disk layout of the Lisa filesystems?

Tom,

Try the following person who I believe has done some work to determine the format of the Lisa file system:

   Natalia Portillo <claunia_at_email.domain.hidden>

From what I understand, there were basically 3 different versions of the Lisa FS which were used by the Lisa operating system. First was a flat FS with a linearly accessed catalog. Second was same flat FS but with hashed catalog. Third was hierarchically based for both catalog and data access. This last FS was later used as a model for the Mac HFS. The MDDF served as the anchor for the FS since it occupied a fixed point on the disk and contained pointers to the other key parts (e.g. catalog, data extents).

There was also a FS format which was used by the Lisa Monitor which served as the Lisa's OS while the real Lisa OS was being developed. The Monitor FS disk format was very similar to the UCSD Pascal disk format. This format is described in one of the Lisa's OS libraries. See page 7 of the attached desktop library interface listing.

Block tags are also important here. Special data structures had special tags. For example, I recall the boot blocks had tag file ID $AAAA. See page 28 in the boot ROM listing for label BOOTPAT. I assume the other FS structures had their own special tags too. It is good to see that the recent Twiggy disk images seem to contain the tag data.

• David Craig
  

===

On January 12, 2014, at 6:33 PM, Tom Stepleton wrote:

> Hi all,
>
> I now have a lot of disk images... and some spare time coming up in airport waiting areas. Seems like a good time to sit down and start poking at the images with Python.
>
> Does anyone have any information about the disk layout of the Lisa file systems, particularly those on Twiggy diskettes?
>
> I've done some experimenting with Ray Arachelian's lisafsh-tool. For a dc42 image of one of the Office System 3.1 install diskettes, the tool is capable of reading the tag file and emitting the list of files on the disk. It reports the following for the format of the disk:
>
> MDDF Volume Name: "Office System 1 3.0"
> Version 0x11: Hierarchial FS with B-Tree catalog Spring Release - 7/7
>
> However, for Twiggy images, here's what I have instead.
>
> MDDF Volume Name: "AOS 3:43 pm 5/06/19"
> Version 0x0e: Flat File System with simple table catalog Release 1.0
>
> It looks like a different type of file system. The "simple table catalog" suggests that the format of the tag file (or equivalent structure) may differ from what's used by the 3.1 diskettes, which may explain why lisafsh-tool reports no files on the disk.
>
> Thanks,
> --Tom

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application/pdf attachment: AppleLisa_-_Desktop_Library_v3_Interface.pdf



application/pdf attachment: AppleLisa-BootROMListing.pdf