The Pentium II ISA maintains full support for executing programs going as far back as the 8080. Feature known as register window. Multiple sets of registers exist and the register CWP keeps track of which set is in use. Renaming some of the registers provides an efficient way of passing parameters between procedures.
Problems occur if the procedures get nested too deeply.
Pairs of these registers can be used to support 128-bit values. All others can only use registers. The byte order is big edian. Make JVM programs downloaded from the Internet much safer to use. The method area, local variables and constant pool are limited to 64 KB each.