Changes
Added link to µPD765 page
Speedlock was also available in disc version.
One version called "[[8k Speedlock]]" relied on the fact that the CPC's hardware (specifically, the [[765 FDC|µPD765 ]] disk controller) could read 8 Kbyte sectors even though it was typically only possible to store more than 6,250 bytes on 300 rpm double density diskettes. Attempting to write an 8 Kbyte sector would cause the system to over-write its header block.
It was written here that "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." This contains several inaccuracies. The Speedlock team in fact wrote the diskettes using diskette interfaces custom-modified for this purpose. Also, an Atari ST also has 6,250 bytes/track although used a WD1772 disk controller, while the PC has over time been based on a variety of formats (e.g. HD was 360 rpm 15 sectors etc.) and controllers (e.g. NEC µPD765 or Intel 8272A or 82072A.
Various methods were attempted to circumvent this protection, including:
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. <br>
