A processing unit executes a vector width instruction in a program and the processing unit obtains and supplies the width of an appropriate vector register that will be used to process variable vector processing instructions. Then, when the processing unit executes variable vector processing instructions in the program, the processing unit processes the variable vector processing instructions using the appropriate vector register with the instructions having the same width as the appropriate vector register. The width that the processing unit obtains may be less than an actual width of the appropriate vector register and may set by the processing unit. In this way, many different vector widths can be supported using a single set of instructions for vector processing. New instructions are not required if vector widths are changed and processing units having vector registers of differing widths do not require different code.