Re: Tips for making Twiggy images

From: Natalia Portillo <claunia_at_email.domain.hidden>
Date: Mon, 16 Feb 2015 17:30:42 +0000

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Hi David,

Oh the date format, is based on what environment you're running it into. While I could hardcode the output I simply did not, so as my system is configured for spanish datetime format (DD/MM/YYYY) shows so, in your system the tool will use us datetime (MM-DD-YYYY) and in Japan it will use japanese one (YYYY/MM/DD).

I can confirm you that the MDDF field for uncooked (user+tag) sectorsize is as documentation says, not as we've got it imaged.

Yesterday I was thinking about how Amiga MFM also have some tag bytes in the header and they include checksums. Maybe the bytes we're not accessing are the checksums, that are transparently checked on read and created on write by the floppy controller.

Why LisaFS needs it I don't know but if you change it, to say 12 bytes, LisaOS will fail to recognize the disk. Anyway LisaFS is quite a mess and from my findings seems to be a mixture of Pascal and asm.

Regards,
Natalia Portillo

P.S.: You can use my tool on any DC42 image you have, including hdd ones. It will recognize LisaFS 1/2/3, Xenix FS, MFS and HFS. UCSD Pascal filesystem is in the TODO list, as well as images of Apple HardDisk 20 that I have not found anywhere (but can be created).

El 16/2/15 a las 17:04, Shirl Casner escribió:

> Hello Natalia,
> 
> Thanks for the MDDF (Media Descriptor Data File) information for
> this Lisa Pascal v1 disk. I am very impressed with what you've
> learned about the Lisa file system structure.
> 
> One suggestion that could make your Disk Image Chef a little better
> is to show dates in format YYYY-MM-DD instead of in DD-MM-YYYY
> format. For example, September 12, 1983 would appear as 1983-09-12
> instead of 12/09/1983 which is confusing for us who are used to
> dates in USA format MM/DD/YYYY.
> 
> Your comment about the Twiggy tag being 24 bytes is interesting, at
> least the MDDF is reporting this as such.
> 
> - David Craig
> 
> ===
> 
> On February 16, 2015, at 1:38 AM, Natalia Portillo wrote:
> 

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>> Hi Tom,
>>
>> I can tell you that the MDDF seems correct:
>>
>> claunia_at_zeus ~ $ mono
>> /Development/DiscImageChef/DiscImageChef/bin/Debug/DiscImageChef.exe
>>
>>
analyze -i ~/Downloads/PascalWorkshop1.0_3of3_682-0051-B.dc42
>> The Disc Image Chef 2.2.5365.5370 Copyright © 2011-2014 Natalia
>> Portillo
>>
>> Image format identified by Apple DiskCopy 4.2. Identified by
>> Apple Lisa File System. LisaFS v1 Volume name: "Pascal.3" Volume
>> password: "" Volume ID: 0x9B8C4DD721000180 Backup volume ID:
>> 0x0000000000000000 Master copy ID: 0x00000000 Volume is number 0
>> of 0 Serial number of Lisa computer that created this volume:
>> 384 Serial number of Lisa computer that can use this volume's
>> software 384 Volume created on 12/09/1983 10:47:05 Some
>> timestamp, says 01/01/1901 0:00:00 Volume backed up on 01/01/1901
>> 0:00:00 Volume scavenged on 01/01/1901 0:00:00 MDDF is in block
>> 41 1683 blocks minus one 1642 blocks minus one minus MDDF offset
>> 1684 blocks in volume 536 bytes per sector (uncooked) 512 bytes
>> per sector 1 blocks per cluster 1643 blocks in filesystem 27
>> files in volume 925 blocks free 128 bytes in LisaInfo Filesystem
>> overhead: 25 Scanvenger result code: 0x00000000 Boot code:
>> 0x00000000 Boot environment: 0x00000000 Overmount stamp:
>> 0x0000000000000000 Volume is clean
>>
>> About the tag size, as you can see the MDDF clearly says there
>> should be 536-512 bytes (that's, 24 bytes in a twiggy tag). In
>> Sonys, it says 20 bytes.
>>
>> But you should think about one thing, that is, how much can you
>> read talking to the floppy controller, and how much it is really
>> stored in the disk. We'll need something like DiscFerret to
>> really know.
>>
>> Really why haven't someone yet taken a cheap ARM Msomething and
>> made one that works in a simple development board, like, say, TI
>> LaunchPad I don't know.
>>
>> Anyway, you got a sep83 disk :p Cheers!
>>
>> My tool can also compare sector by sector and tag by tag of any
>> DC42 image.
>>
>> Free, opensource, http://github.com/claunia/DiscImageChef feel
>> free to use it and bomb me with suggestions.
>>
>> Someday in 2015, if destiny allows, I'll implement reading
>> LisaFS, as I have already decoded it an I'm able to do without
>> using the tags to find the files.
>>
>> Regards, Natalia Portillo
>
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Received on 2015-07-16 12:39:51