Frodo comes in two “flavours” that allow you to decide between speed and accuracy of the emulation.
Frodo works with a cycle-based emulation model. That means that the emulator switches between 6510 and VIC in every emulated ø2 clock phase. By doing this, Frodo achieves a very high precision (nearly all graphical effects can be emulated), but at the expense of speed.
Frodo Lite is a simplified version of Frodo that is line-based, meaning that the activities that happen in parallel during one video line in the real C64 are emulated one after the other for the different chips. This offers an increase in speed at a still reasonable degree of precision of the emulation. There are some things that cannot be emulated with this technique, but it works fine with about 80% of all C64 programs and it is also the faster of the two Frodo versions.
In the settings window, Frodo Lite offers some advanced options which allow control over certain timing aspects of the emulation.