Sony comes out to play

Sony comes out to playRichard Ball and Steve Bush
Sony Computer Entertainment gave details of an impressive sounding media processor at ISSCC.
The 250MHz chip will form the core of Sony’s next Playstation games console.
The device has ten floating point multiply accumulator (MAC) blocks, four floating point dividers and an MPEG2 decoder.
All this is integrated, using 10.5 million transistors, onto a die measuring 240mm2 in a 0.18?m process. Its peak performance is claimed to be 55 million polygons rendered a second.
Sony’s focus has always been in entertainment, and in recent years this has moved to computer products such as games consoles. The company believes the secret to high performance multimedia is to have multiple execution units and wide internal busses.
At the core of the media processor is a MIPS Technologies processor from Toshiba, which controls data over 128-bit busses. The processor is superscalar, issuing two instructions per cycle at 250MHz.
Attached to the bus are two floating point vector co-processors and an image processing unit. A ten channel DMA controller feeds the execution units with data at 125MHz.
The first vector unit (VU0) contains a floating point MAC and divider. The 128-bit wide MAC operates on four 32-bit floating point numbers simultaneously – effectively giving four MACs.
This single instruction, multiple data (SIMD) technique is the same as that used by AMD for its 3DNow! instructions and Intel for its SSE instructions on the Katmai processor. An extra 107 instructions have been added to the MIPS instruction set.
The processor and VU0 are connected by a dedicated 128-bit bus that ties the vector instructions into processor instructions. The two cores can collaborate without interfering with the main bus.
The second vector unit (VU1) mirrors VU0 with the addition of another MAC and divider for geometry calculations. It is VU1 that feeds data via a dedicated 64-bit bus to the external graphics chip.
The image processing unit includes the MPEG2 decoder and carries out colour space conversion from YCbCr to RGB.
The tenth MAC and fourth divider make up the processor’s floating point unit.


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