Each successive architecture standard incorporated more features and took advantage of technology improvements in both software design and silicon manufacturing processes. Starting in 1998, as MIPS Technologies, Inc. became a publicly traded company, MIPS Technologies' architects developed plans for another architecture level. After discussions with system OEMs, development tool vendors, and existing licensees of MIPS Technologies, the team refined their plans to include two new architectures that would incorporate the best features of the past, add standard underlying OS mechanisms, incorporate a set of instructions targeted at embedded applications, and provide a solid framework for future architectural developments. This became the MIPS32TM architecture. The new MIPS64TM architecture took the MIPS IVTM and MIPS VTM ISA as a base and added the standardized privileged mode architecture and a MIPS32TM compatibility mode.
All data manipulations take place in the internal registers that the architecture has in abundance.
There are 32 general-purpose registers and 32 floating point registers. These instruction encodings are illustrated in Figure 2. As shown in Figure 3, the architecture evolved from the original MIPS ITM ISA to the MIPS VTM ISA many years later. In addition, special features that were particularly useful to specific applications were added as Application Specific Extensions or ASEs. These ASEs permitted extensions to the architecture to be added without requiring that they be implemented in all designs.