From: Armin Vogl (Armin.Vogl_at_gmx.net)
Date: 2007-12-04 23:23:07
Hi Pete, I read the infos on your page. I still have a few questions: >We mentioned before that if the drive gets more than two '0' bits in a row, >it clocks in a random '1' bit occasionally. Is it really random ? I mean the 74LS193 is not reset by the BIT_SYNC line in case there are more than two "0" in a row. Is it the variation in rotation speed together with variation in the decoder clock which creates different bytes for each rotation ? The decoder clock defines the "width" of the bit in time and clocks the 74LS193. Would it be enough to have a number of bits on the track that can not be divided by 8 to generate a pattern that changes with each rotation ? This would still not be random, because after a "1" bit is read, the byte that will be read only depends on how long you get "0" bits. But this patternis not random. I think it would look like random if the amount of bits on the track can not be divided by 8. So the question is: does G64 support an amount of bits on a track rather than bytes ? I still don't get what is "weak" about the bits. I don't understand the term "weak bit". It is not that the bits themselves are not stable on the magnetic medium, but it is more that the drive electronics reads a different byte for each rotation, or ? Sorry if I ask questions that have already been answered elsewhere, but I couldn't find a detailed explanation on the web. Thanks Armin ----- Original Message ----- From: "Pete Rittwage" <firstname.lastname@example.org> To: <email@example.com> Sent: Tuesday, December 04, 2007 10:49 PM Subject: Re: Weak Bits >> Hi ! >> >> I would like to know more about weak bits. What are weak bits ? How can >> they >> be stored in the >> GCR file format ? what would be necessary to support weak bits if you >> want >> to emulate the r/w >> head for drive emulation ? > > There is a page on my site detailing most styles of copy protection used > on the C64. Check under the "weak bits" section (but read the rest for > background information) > > http://c64preservation.com/protection > > - > Pete Rittwage > C64 Preservation Project > http://c64preservation.com > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing list
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