CHDs must reside in subfolders named after the parent ROM. For example:
The corresponds to MAME version 0.159 , a snapshot of the emulator from late 2014 to early 2015. While newer versions of MAME exist with higher accuracy, this specific version is widely used as a "balanced" standard for mid-range hardware and Libretro-based systems like RetroArch and Lakka. ROM Set Configuration mame 2014 reference set mame 0159 roms chds verified
Every ZIP file contains 100% of the data needed to run that specific game. This is the largest format (approx. 81.5GB - 83.7GB for ROMs only) but ensures individual games work independently. CHDs must reside in subfolders named after the parent ROM