The 603 is a model of PowerPC processor under the AIM alliance (Apple/IBM/Motorola). The 603 was not known for having impressive performance and the processor appears to have been mostly used for low-cost or portable applications.
The 603e improves performance over the 603 with the expansion and enhancement of the L1 cache. Clock speeds of the 603e typically reached 200MHz.
The 603ev is an improved version of the 603e and allowed for clock speeds up to 300MHz.