| Author: | Pete Rittwage (registered user: 558 posts ) |
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| Date: | Sat, Oct 22nd, 2011 @ 20:26 ( . ) |
It's a "weak bit" protection, meaning it takes advantage of how the 1541 reacts when no flux transitions occur for more than 3 interpreted byte lengths. These disks have this check on track 32, sector 1, I believe. If you zero out that sector in the image, it will pass protection. It expects the data to be different every time it's read (and it tries 8 or 10 times). When you read the disk in, it is not read in as '0' or no flux transitions, you get the 'random' data instead. nibtools tries it's best to detect this and zero it out when remastering, but it's not always enough to pass the protection. You can try to make it more aggressive with the -f[n] switch where [n] is an integer. Larger numbers zero out larger areas around the detected 'weak' parts. |
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