Newsdee wrote:so you mean the .crt file format? (whatever that is)
It might be simpler to convert them into one of the supported formats, such as extracting the PRG files for example.
You can't for some cartridges like the action-replay which caver99 mentions, as that is a a "Freezer" type cartridge ..
@caver99 -- right now the C64 core doesn't support CRT type files unfortunately. It could certainly benefit immensely if someone were to add that.