Vector Unit Architecture for Emotion Synthesis

0272-1732/00/$10.00  2000 IEEE Processors designed for computer entertainment must perform 3D graphics calculations, especially geometry and perspective transformations. In the PlayStation2, we introduced the idea of synthesizing emotion called Emotion Synthesis and devised a new processor architecture to support its graphics demands. The architecture is embodied in the PlayStation2’s Emotion Engine CPU, which uses vector units (VUs) as the key units for floating-point calculations. Emotion synthesis means the real-time synthesis of a computer graphics animation scene that projects a great deal of atmosphere. For example, when a female character walks into a video game scene, her motion must be determined by solving physical equations in response to interactive events instead of replaying prerecorded data. Moreover, differential equations with a large number of variables must be used to describe, for example, the waving motions of her hair in a breeze. For authenticity in emotion synthesis, the CPU must execute these calculations in real time. The Emotion Engine has achieved a peak performance of 5.5 Gflops at an operation frequency of 300 MHz. Its vector units operate in two modes: VLI, for use as a stand-alone processor and coprocessor for use as a MIPS COP2. This arrangement allows a vector unit to simultaneously execute huge amounts of 3D graphics calculations and flexible calculations in collaboration with the CPU core. Both calculation types are indispensable in producing emotion synthesis. By employing software pipelining techniques, a vector unit can execute 3D perspective transformations with seven-cycle throughput at 300 MHz (85 Mvectors/sec). The vector unit in the 0.25micron CMOS Emotion Engine chip contains 5.8 million transistors in 8.76 mm × 7.87 mm.