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Author Topic: dc42 images and known good checksums  (Read 6525 times)

jamesdenton

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dc42 images and known good checksums
« on: April 15, 2025, 09:52:16 pm »

With dc42 images floating around in various working and non-working states, I was curious to know if anyone has compiled a list of (md5?) checksums for known-working dc42 images. This would avoid a copy operation and subsequent failure, and maybe even help reconcile images of varying names to an exact disk. I'm mainly concerned about the legit Apple install media versus random images. Does something like this exist already and, if not, would it be of any use to anyone besides me?
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sigma7

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Re: dc42 images and known good checksums
« Reply #1 on: April 15, 2025, 10:10:54 pm »

would it be of any use?

Yes, I think it would be useful.

My initial inclination would be to md5 only the data (exclude the tags), and to skip the DC42 header.

Further, the catalog would store the value for the ultimately uncompressed data/result (so the md5 value would be the same for a disk image encoded as binary, dc42, zip, sit etc.).

Perhaps two values should be stored, one for the above, and one for the file as-is (including tags and DC42 header after zipping or whatever).
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sigma7

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Re: dc42 images and known good checksums
« Reply #2 on: April 15, 2025, 10:58:14 pm »

With dc42 images floating around in various working and non-working states

Since we recently had an issue with suspected corruption of ROM images on bitsavers, perhaps the reference catalog could include more than just disk images?

ie. also ROM images, including CPU, I/O, expansion boards, P6A & video PROMs, COPS, Widget & ProFile firmware...
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TorZidan

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Re: dc42 images and known good checksums
« Reply #3 on: April 17, 2025, 02:35:20 am »


A thought: instead of collecting checksums of working dc42 image files, why not collect the files themselves? A curated file server with files that have been verified  and confirmed by someone that they work, and perhaps accompanied with installation instructions, hardware specs /emulator specs used for validating.

From my personal experience, most standard Lisa software out there works just fine in LisaEm, meaning that these floppy images are good.
The one thing I found not working was the dc42 image for Lisa Monitor 11.2 (all copies floating around on the web do not boot in LisaEm). But that's fine: there are so many other Lisa Monitor versions, and they work fine.

 
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blusnowkitty

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Re: dc42 images and known good checksums
« Reply #4 on: April 17, 2025, 09:44:40 am »

Start posting MD5s of your DC42s, and I'll start getting them linked into the Apple Lisa Software Release document.
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ried

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Re: dc42 images and known good checksums
« Reply #5 on: April 17, 2025, 09:58:24 am »

Thank you for creating that document. Very helpful! I have a set of BPI Accounting System disks that I've been meaning to archive and make available. Similarly, a friend has come across a bundle of three Twiggy disks for a previously unknown (?) LOS app called Tekalike by Mesa Graphics, dated 1984. Seems to be a terminal graphic program of some sort, and will be shared after I receive them for archiving.
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blusnowkitty

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Re: dc42 images and known good checksums
« Reply #6 on: April 17, 2025, 10:08:49 am »

Similarly, a friend has come across a bundle of three Twiggy disks for a previously unknown (?) LOS app called Tekalike by Mesa Graphics, dated 1984. Seems to be a terminal graphic program of some sort, and will be shared after I receive them for archiving.

Good find, I'm interested to see it in action - it looks like my first thought was correct, this is a Tektronics 4010/4050 graphics terminal emulator program that appears to have gotten ported over to the Mac later in life: https://books.google.com/books?id=zC4EAAAAMBAJ&pg=PA46&dq=%22tekalike%22+mesa+graphics&hl=en&sa=X&ved=2ahUKEwib8fPSnt-MAxXkRTABHZemF_wQ6AF6BAgIEAM#v=onepage&q=%22tekalike%22%20mesa%20graphics&f=false


I also found some snippets on Google Books implying that Tekalike did actually ship for Lisa... the dealer pamphlet also says Mesa Graphics was writing software for Lisa in 1983, think this is what they were writing? http://www.bitsavers.org/pdf/apple/lisa/marketing/Lisa_Dealer_Presentation_1983.pdf
« Last Edit: April 17, 2025, 10:22:58 am by blusnowkitty »
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stepleton

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Re: dc42 images and known good checksums
« Reply #7 on: April 17, 2025, 02:10:24 pm »

LOS app called Tekalike by Mesa Graphics, dated 1984. Seems to be a terminal graphic program of some sort, and will be shared after I receive them for archiving.

Oh I can't wait --- this is highly relevant to some of my other retrocomputing interests:

https://github.com/stepleton/hpgl2tek
https://github.com/stepleton/mupas/tree/main/examples/fourspite
https://github.com/stepleton/mupas/tree/main/examples/perplex
https://www.youtube.com/watch?v=ind_2eMzsbM
https://www.youtube.com/watch?v=3Gm0Cl54dZY
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sigma7

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Re: dc42 images and known good checksums
« Reply #8 on: April 17, 2025, 02:44:49 pm »

Start posting MD5s of your DC42s


BLU 0.10
MD5 (BLU010.dc42) = fd526ea9e045d2024f832c45b7929d29


Xenix 2.3 Twiggies
MD5 (Xenix1of5.dc42) = 1fac4eafbc3567bc50ef5f3a826581d3
MD5 (Xenix2of5.dc42) = 003b436f821c715e57c0ec8d5d61f2fc
MD5 (Xenix3of5.dc42) = 40f71ac5d01e625d384ef51c23362452
MD5 (Xenix4of5.dc42) = 59bdcf071539b610032cb119d9e9f1ea
MD5 (Xenix5of5.dc42) = 40682b206e02b38b3759ad750ac36c28

Modified for X/ProFile per http://sigmasevensystems.com/xpf_xenix.html
MD5 (Xenix1of5Mod.dc42) = fda0c629208de4d812c06878c20cab5b
MD5 (Xenix2of5Mod.dc42) = a7da78e7eff741b473c05903a1b78cba


The Xenix images checksummed above were created with BLU 0.07 (which appears in the DC42 header), so another image of the same disk with a different version of BLU will have a different MD5.
Hence the suggestion to MD5 only the data portion of the DC42, eg:

hexdump -v -e '"%X"' -s 84 -n 871424 Xenix1of5.dc42 | md5 = 1c5935aa5eb3aec6b32d160a2349d97d
hexdump -v -e '"%X"' -s 84 -n 871424 Xenix2of5.dc42 | md5 = e3ab77488bb12de3ecd68fb0e9d56d32
hexdump -v -e '"%X"' -s 84 -n 871424 Xenix3of5.dc42 | md5 = 4fe11fefe374e319b1a0552f0e190202
hexdump -v -e '"%X"' -s 84 -n 871424 Xenix4of5.dc42 | md5 = 90251cf641728321277f3b15ce0b948c
hexdump -v -e '"%X"' -s 84 -n 871424 Xenix5of5.dc42 | md5 = 6dfac516dc2b0ddd49ab01ad939478ca

where "-s 84" skips the first 0x54 bytes (the DC42 header) and "-n 871424" considers only the 0xd4c00 bytes of data (excluding the tags).
the md5 is performed on the hexdump, which I used only for the convenience of it having -s and -n parameters.

The decimal number of data bytes in a non-sparse DC42 image are
Twiggy 871424
400k 409600
800k 819200

edit: added hexdump suggestion example
« Last Edit: April 17, 2025, 05:02:39 pm by sigma7 »
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blusnowkitty

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Re: dc42 images and known good checksums
« Reply #9 on: April 17, 2025, 03:38:46 pm »

When did XENIX 2.3 show up?
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sigma7

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Re: dc42 images and known good checksums
« Reply #10 on: April 17, 2025, 04:50:53 pm »

When did XENIX 2.3 show up?
The dates on the files are 2011, is it actually 2.3 as the folder is named? Dunno. I thought these were on BitSavers, but I don't see them in the Twiggy folder.
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stepleton

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Re: dc42 images and known good checksums
« Reply #11 on: April 17, 2025, 07:29:59 pm »

Twiggy Xenix is new to me too. Google turns up no hits for "Xenix5of5.dc42".
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TorZidan

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Re: dc42 images and known good checksums
« Reply #12 on: April 17, 2025, 08:53:40 pm »

... Hence the suggestion to MD5 only the data portion of the DC42, eg ...

This is getting hairy because twiggy and sony400 and sony800 images have different data size. Also, an image like https://github.com/stepleton/LisaMandelbrot/blob/master/Solo/LisaMandelbrot_twiggy.dc42 is just 1KB, and is still a valid dc42 image (with just two sectors).

Instead of this md5 madness, why not use the 4-byte data checksum that is already calculated and stored in the dc42 header?
It is always at offset 72:
Example how to get it in Linux:
Code: [Select]
dd if=BLU090.dc42 bs=1 skip=72 count=4 status=none | xxd -p
1858813c


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sigma7

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Re: dc42 images and known good checksums
« Reply #13 on: April 18, 2025, 01:54:11 am »

This is getting hairy ...

Agreed, but:

The checksum is not always valid; some dc42 files have a zero checksum indicating it was not calculated...

- Floppy EMU does (or did) this because recalculating on the fly is not practical (maybe images edited by Floppy EMU won't ever be a consideration, but I think it isn't impossible for someone to create a valuable image via FEMU).
- I have a couple of older images that predate BLU and Floppy EMU that have zero checksums; I don't know what software created them.

Others have an incorrect checksum because eg. someone has edited the data... possibly the best reason to MD5 is to confirm the data integrity vs identify the image

The variable file length is a complication -- the data length could be extracted from the dc42 header, eg. in the same way you extracted the checksum, and this should work for the sparse images too.

« Last Edit: April 18, 2025, 01:57:19 am by sigma7 »
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ried

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Re: dc42 images and known good checksums
« Reply #14 on: May 06, 2025, 01:56:33 am »

Good find, I'm interested to see it in action - it looks like my first thought was correct, this is a Tektronics 4010/4050 graphics terminal emulator program that appears to have gotten ported over to the Mac later in life: https://books.google.com/books?id=zC4EAAAAMBAJ&pg=PA46&dq=%22tekalike%22+mesa+graphics&hl=en&sa=X&ved=2ahUKEwib8fPSnt-MAxXkRTABHZemF_wQ6AF6BAgIEAM#v=onepage&q=%22tekalike%22%20mesa%20graphics&f=false


I also found some snippets on Google Books implying that Tekalike did actually ship for Lisa... the dealer pamphlet also says Mesa Graphics was writing software for Lisa in 1983, think this is what they were writing? http://www.bitsavers.org/pdf/apple/lisa/marketing/Lisa_Dealer_Presentation_1983.pdf

Just added DC42 (BLU 0.9) Twiggy disk images for all three disks to the files section: https://lisalist2.com/index.php/topic,629.0.html
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