: For MAME to recognize them, CHD files must be placed in a subfolder within your ROMs directory. This subfolder must have the exact same name as the game's ROM zip file.
MAME expects the CHD to be inside a with the exact same name as the ROM zip (minus the .zip extension). If the CHD is missing or placed incorrectly, the game will not boot. mame roms chd
Think of an arcade cabinet as a computer. The contains the BIOS and the operating system instructions (the ROMs on the motherboard). The CHD file contains the hard drive or disc inserted into that computer. : For MAME to recognize them, CHD files
CHDs contain the raw data from these storage devices. Examples include: : For MAME to recognize them