Gaming Nostalgia: Unveiling the Challenges of Copy-Lock Protection

New research by GloriousCow delves into the fascinating world of historical floppy disk copy protection schemes, unveiling the first of their investigations into Formaster’s Copy-Lock. This particular scheme was used in the early days of the IBM PC, with one notable example being the popular game King’s Quest by Sierra Entertainment.

Unlike other copy protection methods that required users to boot DOS separately, the Copy-Lock protection scheme allowed for the automatic launch of the game simply by inserting the designated floppy disk. The Copy-Lock employed various techniques to make it difficult for the standard floppy disk hardware to replicate.

One of the tactics employed by Copy-Lock was the intentional alteration of Sector 1 on track 6. Instead of the standard 512-byte sector, this sector was written as only 256 bytes, with a 256-byte blank section to fill the gap. Furthermore, the CRC (cyclic redundancy check) values of the sector were also tampered with, adding an additional layer of protection.

This unique disk structure posed a challenge for PCs attempting to read the disk. The PC BIOS interrupt routine, assuming a standard 512-byte sector, fails to locate the altered sector when a “read sector” command is issued. To detect unauthorized copies, the game bypasses the BIOS and directly communicates with the floppy disk controller using custom code.

The game’s code initiates the seeking of track 6, sector 1, using the standard INT 13h routine, expecting a failure due to the absence of a valid sector. By sending the “read track” command and examining the final byte for a specific magic number, 0xF7, the game confirms the presence of Copy-Lock protection. Importantly, this unique disk structure cannot be created with a standard IBM PC floppy disk controller, requiring specialized hardware that can write different-sized sectors and incorrect CRCs.

This investigation by GloriousCow is a testament to the ingenuity of early copy protection methods and the challenges they posed for both game developers and pirates alike. If you’re interested in preserving these digital relics or learning more about the complex world of floppy disk copy protection, be sure to check out GloriousCow’s ongoing research.

– One key challenge with copy-lock protection schemes was the need for specialized hardware that could write different-sized sectors and tamper with CRC values, making it difficult for standard floppy disk hardware to replicate.
– The Copy-Lock protection scheme used by Formaster allowed for the automatic launch of a game by simply inserting the designated floppy disk, eliminating the need for users to boot DOS separately.
– The intentional alteration of Sector 1 on track 6, with a smaller size and tampered CRC values, was one of the tactics employed by Copy-Lock to make it difficult for unauthorized copies to be made.
– The game bypassed the PC BIOS and directly communicated with the floppy disk controller using custom code to detect unauthorized copies.
– GloriousCow’s research highlights the ingenuity of early copy protection methods and the challenges they posed for both game developers and pirates.

Advantages of copy-lock protection:
– Copy-lock protection schemes provided a level of security for game developers against unauthorized copying and distribution of their games.
– Automatic launch of games by inserting the designated floppy disk made the gaming experience more convenient for players.

Disadvantages of copy-lock protection:
– Copy-lock protection schemes required specialized hardware, making it more difficult for players to create backup copies of their games or for legitimate users to migrate their games to different platforms.
– Copy-lock protection schemes could sometimes lead to compatibility issues with certain hardware or operating systems.

Key challenges associated with copy-lock protection schemes:
1. Compatibility: Copy-lock protection schemes often required specialized hardware, which could lead to compatibility issues with different computer systems or floppy disk controllers.
2. Replication: Copy-lock schemes posed a challenge for pirates to replicate or bypass, requiring sophisticated techniques and equipment.
3. Migration: Copy-lock protection made it difficult for legitimate users to migrate their games to different platforms or make backup copies, limiting their ability to preserve and enjoy their purchased games in the long term.

Controversies associated with copy-lock protection:
– Copy-lock protection methods were considered a necessary measure by game developers to protect their intellectual property, but some players and enthusiasts argue that these protection schemes hindered the preservation and accessibility of historical games.

For more information on this topic, you can visit GloriousCow’s ongoing research on floppy disk copy protection at: GloriousCow

The source of the article is from the blog newyorkpostgazette.com