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Questions tagged [copy-protection]

For questions about copy protection techniques used on retro software.

3
votes
3answers
268 views

How can I view BASIC code hidden by SYS?

I ran a validation of an old disk, and it turns out this ruined a game (won't load) and deleted my old high score list on David's Midnight Magic. I would like to edit the code to get the high score ...
4
votes
0answers
368 views

Rainbow Technologies Ltd DRM system for DOS

A number of games from the early 1990s appear to be protected with a DRM system developed by Rainbow Technologies Ltd. The system allows content in the games to be unlocked by sending the manufacturer ...
6
votes
4answers
527 views

Was the Amstrad's file protection considered secure in 1985?

I just reverse engineered the file protection on the Amstrad CPC, which uses two sequences of rotating bytes taken straight out of the AMSDOS ROM to XOR each byte of the file. If you have SEQa of 13 ...
9
votes
2answers
519 views

How was Prince of Persia “better/faster” with RWTS18?

I was reading about Prince of Persia over at POP Code Review. In that article, the writer printed an interview with Roland Gustafsson, the inventor of RWTS18 copy protection for the Apple II series. ...
7
votes
3answers
331 views

Advantages to installing a parallel port in a C1541-family drive other than speed

Are there any advantages to installing a parallel port in a C1541-family drive and using a parallel cable to a PC to image disks, other than increased speed (i.e. since the standard IEC protocol is ...
18
votes
3answers
982 views

How did “full memory” Spectrum tape copiers work?

There are some tape copiers, such as LERM that claim to be able to copy tapes which contain software that takes the full 48kbyte of RAM. However, this seems impossible on a Spectrum, when the whole ...
27
votes
1answer
1k views

How does “bit-slip” copy protection work?

Some Apple II 5.25" floppies used a special pattern of bytes that could not be automatically detected by disk copying software. How could the pattern be invisible to disk copiers but detectable by ...