Nintendo S-SMP

The Nintendo S-SMP is the audio processing unit of the Super Nintendo Entertainment System (SNES) video game console.

The S-SMP audio processing unit consists of an 8-bit SPC700, a 16-bit DSP, 64 kB of SRAM shared by the two chips, and a 64 byte boot ROM. The audio subsystem is almost completely independent from the rest of the system: it is clocked at a nominal 24.576 MHz in both NTSC and PAL systems, and can only communicate with the CPU via 4 registers on Bus B. It was designed by Ken Kutaragi and was manufactured by Sony.

The Sony SPC700 is the S-SMP's integrated 8-bit processing core manufactured by Sony with an instruction set similar to that of the MOS Technology 6502 (as used in the Commodore 1541 diskette drive and the Vic 20, Apple II, BBC Micro and in modified form in the original NES).

It is located on the left side of the sound module. It shares 64 KB of PSRAM with the S-DSP (which actually outputs the sound) and runs at 2.048 MHz, divided by 12 off of the 24.576 MHz crystal. It has six internal registers, and can execute 256 opcodes. The SPC700 instruction set is quite similar to that of the 6502 microprocessor family, but includes additional instructions, including XCN (eXChange Nibble), which swaps the upper and lower 4-bit portions of the 8-bit accumulator, and an 8-by-8-to-16-bit multiply instruction.

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