What is the maximum speed of data cat5 cable?

The transmission speed of the cable is limited in most cases by the hardware attached to it.

Cat5 basic cable has been used successfully up to 1 gigabit speed using ethernet. There have been lab tests proving it might be useful for 10gigabit over short ranges but usually that requires Cat5e or Cat6 grade cable.

The most common speeds are 10/100 mb ethernet.