Difference between revisions of "Speedlock"
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One version called "[[8k Speedlock]]", relied on the fact that the CPC's hardware could reliably read but not write 8k sectors. | One version called "[[8k Speedlock]]", relied on the fact that the CPC's hardware could reliably read but not write 8k sectors. | ||
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| + | the format was either devised or done on an Atari ST or an IBM PC compatible machine (since the CPC share with them the same FDC controler). The main difference being that an ST or PC can write more data per track than a CPC. | ||
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| + | In itself, a speedlock track exists in 2 versions, used at the discretion of the duplicator, one use a CRC, and the other not. | ||
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| + | A speedlock track consist of only 512 byte declared for the sector, and all the remaining data is spanned in a huge GAP section. | ||
| + | When copied on a CPC, the FDC only store the 512 first bytes as declared in the CHRN, and discard the remaining contained in the gap section. Those tracks have an EDC (Error Data Checksum), because only 512 bytes are used to calculate the data checksum, as well as an illegal data field size. | ||
There were two methods to get around this: | There were two methods to get around this: | ||
Revision as of 15:24, 19 December 2015
Speedlock is the name of a disc and cassette copy protection designed by Dave Looker (DJL) and Dave Aubrey-Jones.
Earlier versions mentioned "DJL Software" later versions mentioned "Speedlock Associates".
Cassette
It was a modified version of the Spectrum's cassette routines with protection added.
It is often recognised for it's blue/black stripes in the border during loading.
Later versions had multicoloured stripes for the leader/pilot tone, and then blue/black stripes for the data.
As the protection system continued to evolve, programs such as Soft-Lok and the Bonzo Blitz were upgraded to break the protection.
Disc
Speedlock was also available in disc version.
One version called "8k Speedlock", relied on the fact that the CPC's hardware could reliably read but not write 8k sectors.
the format was either devised or done on an Atari ST or an IBM PC compatible machine (since the CPC share with them the same FDC controler). The main difference being that an ST or PC can write more data per track than a CPC.
In itself, a speedlock track exists in 2 versions, used at the discretion of the duplicator, one use a CRC, and the other not.
A speedlock track consist of only 512 byte declared for the sector, and all the remaining data is spanned in a huge GAP section. When copied on a CPC, the FDC only store the 512 first bytes as declared in the CHRN, and discard the remaining contained in the gap section. Those tracks have an EDC (Error Data Checksum), because only 512 bytes are used to calculate the data checksum, as well as an illegal data field size.
There were two methods to get around this:
1. A hardware modification to the Amstrad CPC and a special copy program
2. Executioner's utility Xexor included a 'brain file' solution to crack individual games before copying them.
