Follow these rules, or bad things will happen!
Don’t mix ROMs for different platforms - use generic BASIC with generic KERNAL, Ultimate64 BASIC with Ultimate64 KERNAL, etc.
Don’t mix these ROMs with any other ROMs; exceptions:
kernal_hybrid*.rom, which is meant to be used (and has to be used) with the original BASIC ROM; however, these hybrid ROMs cannot be distributed due to legal/copyright reasons; see here for instruction how to create them
chargen_*.rom - these ones are fully interchangeable
Don’t mix ROMs from different builds/versions (again, CHARGEN is an exception).
The generic ROM set should be compatible with any C64-compatible machine; platform-specific ROMs might not work on other platforms.
For Ultimate 64 motherboard the following settings are recommended:
The *_crt ROM set is a special version, with some code moved to external ROM on the cartridge - thus, more features could be enabled. It needs all the 3 files (BASIC, Kernal, cartridge) to be operable.
Have fun!
PXL font was created by Retrofan, we got a permission to include it with Open ROMs under GNU Lesser General Public License 3.0, see here.