Bad sectors on first 10 tracks with key disk protection

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hydr0x
Posts: 104
Joined: Wed Dec 29, 2010 4:01 pm

Bad sectors on first 10 tracks with key disk protection

Post by hydr0x »

I have three 5.25 floppy games which all show similarl weird behavior when dumping preservation + 5.25 DD MFM.

Image Image Image

As you can see, all of them show bad tracks / sectors for the first 10 tracks. It's a consistent 3 bad sectors per track, which, even to me, suggested some kind of copy protection. Lemmings is a known title with CP and indeed, the other two also use key disk protection. So I know I'll never get a 100% working raw image. No problem.
However, what really irks me is that the files on the created raw images are not okay. For Lemmings and 3D Pool, I have old backups of the same disks done with WinImage. If I compare these images, I can see that there's garbage data in some files on the KryoFlux-created RAW images which is not present on the simple images from back then. E.g. a .bat file contains garbled text instead of proper commands.

Any ideas what's happening here? I'm pretty sure I should be able to get identical raw images to my old ones, but I can't. It seems highly unlikely that all three disks developed the same kind of flaw since dumping them a few years ago. I have also dumped a few dozen other games today using the same drive with no similar problems.

I can of course provide stream files if needed :)

hydr0x
Posts: 104
Joined: Wed Dec 29, 2010 4:01 pm

Re: Bad sectors on first 10 tracks with key disk protection

Post by hydr0x »

Just found some older dumps (all 5.25 DD with suspected key disk protection) showing the exact same pattern, namely Conflict: Europe and 4D Sports Boxing.

SomeGuy
Posts: 252
Joined: Wed Feb 18, 2015 8:18 pm

Re: Bad sectors on first 10 tracks with key disk protection

Post by SomeGuy »

What has probably happened is that WinImage "sanitized" the data - replacing bad sectors with empty data and avoided reading any extra sectors. DTC tends to just throw everything it thinks it can read in to an image file - technically preferable for preservation, but can result in a mess.

Of course, sector images are not going to be of much use when copy protection is involved.

If you write the Kryoflux streams back to disk, a real computer running DOS will see all of the files fine.

NRS
Posts: 27
Joined: Mon May 06, 2013 8:32 pm

Re: Bad sectors on first 10 tracks with key disk protection

Post by NRS »

Try limiting the maximum sector count to 9 in the MFM format settings. This will skip the copy-protected sectors from being included in the MFM image, though not in the stream files. That the BAT file contains garbled sectors is more likely the result of additonal sectors getting in the way, so that the sectors aren't read from where they're supposed to be, since .IMA files have no metadata whatsoever.

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IFW
Posts: 3079
Joined: Mon Nov 08, 2010 2:42 pm

Re: Bad sectors on first 10 tracks with key disk protection

Post by IFW »

Thanks NRS and SomeGuy :)
In addition to what they said: you do get a 100% raw image, that is the stream file. Any other format is just derived from the sampled flux reversal data stored in the stream files.

hydr0x
Posts: 104
Joined: Wed Dec 29, 2010 4:01 pm

Re: Bad sectors on first 10 tracks with key disk protection

Post by hydr0x »

Thanks NRS, limiting to 9 sectors does indeed produce a "working" image with correct files.

@IFW well, that's obvious, but considering tool support for IBM stream files, it doesn't really help

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