Just a few years ago embedded processors were merely hand-me-downs from the PC world: obsolete PC processors, recycled as embedded processors. But this picture has changed almost completely. Today more and more embedded processors are specifically designed for the embedded market.

This became very apparent at the recent Embedded Processor Forum in San Jose, CA. The very informative event was put on by Cahners MicroDesign Resources, the same folks who also organize the Microprocessor Forum. In the category 'High-Performance Processors for Embedded Systems' only one of the six presenting companies actually showed a variation of a desktop CPU design.

The trends in embedded processor design are clearly moving towards new CPU architectures, chip multiprocessing (CMP), i.e. multiple CPU cores on a single die, and high performance (clock speeds up to 1 GHz!). The latter is definitely needed for some embedded applications that have an almost insatiable hunger for high performance. For example home video-game consoles, advanced set-top boxes, HDTVs, network routers, switches, gateways, and broadband modems - just to name a few.

New Architectures

Some of the embedded processors borrow technology from PC processors to gain more performance. They implement superpipelining for high clock speeds, and superscalar pipelines for parallel execution. Others developed new technologies that have not been seen in PC processors yet: CMP, integrated DSPs, embedded DRAM, VLIW, 64 bit RISC, and specialized data-path architectures. On top of that, embedded processors offer more options and are customizable, while in case of the desktop/server CPUs the vendors pretty much decide what you need and get. With some embedded processors on the other hand, customers can choose cache sizes, pick functions units, add on-chip memory (SRAM, embedded DRAM), and configure I/O components. Licensable cores also enable high integration.

Cahners MicroDesign Resources did a good job of inviting quite a diverse group of companies to present at the Forum. Quite interesting was for example the MIPS64 20K family of processor and core designs from MIPS Technology. The R20K processor and 20Kc core were originally conceived for servers and workstations, but then redesigned for high-performance embedded applications. MIPS implemented extensions to accelerate 3D geometry processing for digital entertainment applications: the chip comes with 6 integer units and a SIMD FPU, two 32 kB 4-way set associative on-chip caches, delivers 30 million polygons/s (1200 MIPS, 2.4 GFLOPS) at 500 MHz, and has an estimated power dissipation of 0.09 mW/MHz/mm².