R4300i

The R4200 is a microprocessor designed by MIPS Technologies, Inc. (MTI) that implemented the MIPS III instruction set architecture (ISA). It was also known as the VRX during development. The microprocessor was licensed to NEC, and the company fabricated and marketed it as the VR4200. The first VR4200, an 80 MHz part, was introduced in 1993. A faster 100 MHz part became available in 1994. The R4200 was developed specifically for low-power Windows NT computers such as personal computers and laptops. MTI claimed the microprocessor's integer performance was greater than that of a high-end Intel i486 and 80% of a P5-variant Pentium microprocessor. The R4200 ultimately did not see any use in personal computers and was repositioned as an embedded microprocessor that competed with the R4600. The R4300i variant was used in the widely popular Nintendo 64 video game console.

The R4200 is a scalar design with a five-stage classic RISC pipeline. A notable feature is the use of the integer datapath for performing arithmetic operations on the mantissa portion of a floating point number. A separate datapath was used for the exponent. This scheme reduced cost by reducing the number of transistors, the size of the chip, and power consumption. It also impacted floating point performance negatively, but the R4200's intended applications did not require high floating point performance.

The R4200 has a 16 KB instruction cache and an 8 KB data cache. Both caches are direct-mapped. The instruction cache has a 32-byte line size, whereas the data cache has 16-byte line size. The data cache uses the write-back write protocol.

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