Reality Signal Processor

The Reality Signal Processor, or RSP, is the portion of the RCP responsible for matrix math, lighting calculations, clipping, shading, and other highly parallel graphics tasks as well as audio processing.

It is made by a stripped-down MIPS 32-bit core (without a few more advanced opcodes) referred to as Scalar Unit (SU), composed with a coprocessor (configured as COP2) that can perform SIMD operations on a separate set of vector registers, referred to as Vector Unit (VU).

RSP has two different banks of onboard dedicated memories: IMEM (4KB) for instructions, and DMEM (4KB) for data. It has no external memory buses but has a DMA engine capable to copy code/data from/into DMEM/IMEM and the main RDRAM. The DMA engine can be driven by either the main CPU or the RSP itself.

The code running on the RSP is usually called "microcode", but it's a standard MIPS program, obviously containing the dedicated COP2 instructions to drive the VU. The RSP can be programmed in custom microcode to handle specific tasks, though most commercial games leveraged one of several stock microcodes made available by Nintendo at the time.