CHD files typically reduce file sizes by 40% to 60% compared to uncompressed BIN/CUE files.
If you are using an older version (like the popular 2.0.5), you will not see CHD files in the "Run ISO" list, and you must update the emulator from the official ePSXe website to gain this feature. epsxe chd files
Support for ISOs in CHD format was added in ePSXe version 2.0.18 . CHD files typically reduce file sizes by 40%
Since most PS1 ROMs are still distributed as BIN/CUE pairs, you will likely need to convert them yourself using a tool called . 1. Using CHDMAN (PC Method) epsxe chd files