Re: Lisa Hardware Interface 9.1 source

Hello David,

Thank you very much for your Python utility which extracts files from Apple Lisa monitor formatted disks, looks very well done.

One potential problem with this file extraction utility is from my reading is it does not seem to support Monitor disks which have the extended directory structure. Normally, these disks held a maximum of 77 files per the Monitor's UCSD Pascal legacy, but Apple added an extended directory which supported 787 files and is documented in the VOLMGR.OBJ object file that is part of the Lisa hardware interface source. The portion of the VOLMGR.OBJ which shows the interface section for this object file discusses the two directory types:

{ there are two types of directories, small ones and big ones.   a small one takes up 4 blocks, and can store entries for 77    files (+ 1 for the directory entry). a big one occupies 40    blocks, and can store 786 (+1) entries. }

I suspect the extended directory structure was used mostly for ProFile (5MB) and Corvus (10MB) hard drives which were used for Apple's internal Lisa software development effort. Having 77 files on a hard drive seems like lots of disk space would be unused. This extended directory structure may also have been used on the 860KB Twiggy disks. I recall that the Monitor programmer's manual talked about how to format the disks to support this larger directory structure.

Your utility, if it does not already support this extended directory structure, may I think be more useful if it did. Key to supporting this structure is to not assume a fixed length for the directory. Use the number of allocated directory blocks to determine the max number of files supported. This will generally be a 4 block directory.

Also ... I recall several disks which Apple released for the Lisa public used the Monitor disk format:

     LisaTest
     LisaGuide  (not 100% sure here)
     MacWorks

Also, also ... I recall reading in Apple's internal Lisa development materials that a Lisa could format a disk to contain both a Lisa OS and Monitor file structure. I suspect obtaining such disks would be very very very rare. Determining the low-level structure details would involve some work. The attached LISA MONITOR v10.0 release note dated July 15, 1982 discuss this extended directory structure.

Thanks for your Lisa efforts, appreciated. Hope these comments are of some practical use.

Regards,
David Craig

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===



> On May 5, 2016, at 7:53 AM, David Ryskalczyk <d235j.1_at_email.domain.hidden> wrote:


> 

>> 
>> I can post this to GitHub in a "lisa tools" type repo, if anyone is interested.


> 

> Posted to https://github.com/d235j/lisa-utilities/. Already one bugfix — the code that printed out file types wasn't completed and would print out incorrect data. This did not affect file extraction, though.


> 

> Regarding the question about IDLE and ProFile drives — this is specifically in regards to the Lisa I.

> Additionally it seems that Lisa Monitor does not have a way to unclamp the drive from software, which means I cannot get IDLE to save a modified image.

> 

> David


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application/pdf attachment: LISA_Monitor_10.0_Release.pdf