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Old 21 March 2020, 22:10   #1
solarmon
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Secret of Monkey Island - disk images CRC32 values?

Hi,

I have two physical sets of Secret of Monkey Island disks, that were acquired separately, that I want to make sure they are restored to original.

I'm using Greaseweazle to dump the images to SCP format and then using HxC Emulator Software to check the image and view the CRC32 checksum of it to compare with the original IPF versions.

However, the two physical sets I have don't seem to match, CRC32 wise, to any of the IPF originals.

The IPF originals I have compared against have been take from the TOSEC sets on the EAB FTP server (and also checked/compared against the IPF image sets on archive.org).

Below are the CRC32 checksums that the HxC software shows for the IPF originals and the dumped SCP disk images.



The 1st disk of the physcal disks sets don't have the same checksum. This may be because they may have been altered in some way if they did not have their write protect tabs set. But you can see that disks 2, 3 and 4 all have the same checksum - so I'm confident that these sets of disks were duplicated/mastered from the same source images.

However, they do not match any of the IPF original sets. I was assuming/hoping that that should match the EN set.

I can tell by the dumped images that that were not created/copied/duplicated on an Amiga - the tracks are index aligned (on an Amiga, I understand that the tracks are not aligned with the index when they are written).

Maybe the disks were written using Kyroflux or SuperCard Pro? But both sets have the same checksums (apart from disk 1).

Why/how would my physical disk sets have a different CRC32 checksum to any of the original IPF sets?

Thank you!

Edit: These are the IPF images:

Secret of Monkey Island, The v1.2 (1991)(Lucasfilm)[1625]
Secret of Monkey Island, The D1.2r (1991-03-26)(Lucasfilm)(DE)[0359]
Secret of Monkey Island, The v1.0 (1991-04-26)(Lucasfilm)(FR)[1750]
Secret of Monkey Island, The v1.0 (1991-07-02)(Lucasfilm)(IT)[2322]

Last edited by solarmon; 21 March 2020 at 22:19.
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Old 21 March 2020, 22:53   #2
jotd
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this game doesn't have any physical protection. If the files are the same as others IPF it should be enough. Comparing files is probably much easier than comparing IPFs

one other thing you can do is to convert ipfs to adfs and check adfs. Maybe bootsector is different.
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Old 22 March 2020, 07:50   #3
solarmon
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Quote:
Originally Posted by jotd View Post
this game doesn't have any physical protection. If the files are the same as others IPF it should be enough. Comparing files is probably much easier than comparing IPFs

one other thing you can do is to convert ipfs to adfs and check adfs. Maybe bootsector is different.
My physical sets of disks boots and work fine. I just want to make sure it is fully restored to the original master images - I'm OCD like that.

I can/could restore all 4 disks to use the IPF EN images, but I was curious as to why my two physical disk sets seem to have a different set of CRC32 checksums.

Since the IPF EN set is labelled as being 'v1.2' I assume there must/could have been a 'v1.0' version?
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Old 24 March 2020, 09:57   #4
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I did a bit more digging and the reason the CRCs are different is because they have different 'root blocks'. Specifically, the timestamps are differrent.

For example, for disk four:

IPF Image:
Created: Wed Mar 13 14:59:10 1991
Last altered: Wed Mar 13 15:01:56 1991

SCP Dump:
Created: Fri Mar 22 16:36:06 1991
Last altered: Fri Mar 22 16:38:52 1991

I don't know why my physical disks sets have the same timestamps but are different from the original IPF sets.

I'd be interested in other peoples disks sets dumps and what CRC and timestamps they have.
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