Ricoh 5A22

From Wikipedia, the free encyclopedia

The Ricoh 5A22 is the microprocessor CPU produced by Ricoh for the Super Nintendo Entertainment System (SNES) video game console. The 5A22 is based around the 16-bit CMD/GTE 65c816, itself a version of the WDC 65C816 (used in the Apple IIGS personal computer).

All of the above mentioned processors are based on the MOS Technology 6502 family of processors.

[edit] Major features

In addition to the 65C816 CPU core, the 5A22 contains support hardware, including:

Controller port interface circuits
Circuitry for generating NMI interrupts on Vblank
Circuitry for generating PSG sound with included 2A03 core
Circuitry for generating IRQ interrupts on screen positions
A DMA unit, supporting two primary modes:
- General DMA, for block transfers at a rate of 2.68MB/s
- Hblank DMA, for transferring small data sets at the end of each scanline outside of the active display period
Multiplication and division registers

[edit] Performance

The CPU as a whole employs a variable-speed system bus, with bus access times determined by the memory location accessed. The possible clock speeds are 1.79, 2.68 and 3.58 MHz. For most purposes, however, the bus runs at 2.68 MHz and drops to 1.79 MHz when accessing certain PPU registers. It works at approximately 1.5 MIPS (using strictly 16-bit instructions) and has a theoretical peak of 1.79 million 16-bit adds per second.