Mitsubishi Electric Co Ltd is wooing interactive television set- top box makers to incorporate its M32 microprocessor – a chip that includes around 16Mb of dynamic random access memory on board. The M32 is the first of a new breed of microprocessors due to come out from a variety of manufacturers this year. Using an idea pioneered by the Inmos International Ltd Transputer, the new breed will include large quantities of on-board memory for video and graphics processing. The on-chip DRAM offers greater memory bandwidth than can be achieved by the traditional model of a CPU accessing memory via an external interface. Bandwidth such as is given by on-board DRAM is desperately needed for the real-time compression and decompression functions of three-dimensional graphics and high speed video processing requirements found in many multimedia applications. As well as set-top boxes, the microprocessors are expected to be used in Personal Digital Assistants, arcade games machines and multimedia systems. The integration of DRAM and a RISC core on a single chip boosts system performance to a totally new level and opens market opportunities that were not feasible, Mitsubishi’s Ike Saeed is quoted as saying. The chip also has a 16K-bit static RAM cache. Connecting the static and dynamic memory and the 32-bit RISC processor core is a 128-bit internal bus. Key to the architecture is the very small core – only 2mm by 2mm – with 16-word by 32-bit general-purpose registers. At 66MHz the chip delivers performance benchmark ratings of 52.4 Drhystone MIPS and performs most common instructions in one clock cycle, four types of multiply and accumulate instructions with 64-bit accumulator and compound load-store instructions so that it can function comfortably as a 16-bit fixed point signal processor.
