You can't see them, but they're everywhere, exerting more and more influence on our lives, sometimes spelling the difference between life and death. We're talking about embedded microprocessors: the hidden chips that control everything from cell phones and microwave ovens to jumbo jets and antilock brakes.
Processors for PCs, workstations and servers get all the attention, but embedded microprocessors make the world go 'round.
In terms of unit sales, PC processors like Intel Corp.'s Pentium series; Sunnyvale, Calif.-based Advanced Micro Devices Inc.'s Athlon; and IBM and Schaumburg, Ill.-based Motorola Inc.'s PowerPC account for only 6 percent of the world market, according to audited reports in the World Semiconductor Trade Statistics' blue book. The remaining 94 percent - 5 billion chips - consists of embedded microprocessors.
That startling statistic is more understandable when you realize how pervasive microprocessors have become. It's estimated that the average U.S. household has about 60 embedded microprocessors.
Some embedded microprocessors are hand-me-downs from the desktop market - chips that are obsolete for today's PCs but perfectly adequate for less-demanding tasks. The Z80 and 6502 processors that powered early PCs like the TRS-80, Apple II and Commodore 64 are still big sellers. In fact, 8-bit processors outsell the latest 32- and 64-bit processors by a 10-to-1 margin. Even the most feeble 4-bit processors far outsell 32-bit processors like the Pentium. Old microprocessors rarely die, and they hardly ever fade away - they just become embedded.
As a result, the embedded-microprocessor market is unusually broad. At any given moment in the PC market, microprocessors span a performance range of only about 3 to 1 - the fastest chips currently run at 1 GHz (1,000 MHz), while the slowest commonly available chips are about 333 MHz. In contrast, the performance range just for 32-bit embedded microprocessors is 500 to 1. If you factor in the 4- and 8-bit processors, the performance range is thousands to one.
Despite having thousands of off-the-shelf chips to choose from, many product designers need something unique. So they create their own embedded chips, called application-specific integrated circuits.
A designer starts by licensing an embedded-microprocessor core from a company such as U.K.-based ARM Holdings PLC or Mountain View, Calif.-based Mips Technologies Inc. and then adds features specific to his application. For a digital-camera processor, he might add a controller for the charge-coupled device chip; for an Internet-enabled appliance processor, he might add an Ethernet interface.
The designer takes the design to a foundry - a company that owns "fabs" (chip factories) and sells part of its manufacturing capacity to other companies.
Popular fabs are United Microelectronics Corp. and TSMC in Taiwan and IBM Microelectronics in the U.S.
Customizable Processor Cores
Even that flexibility isn't enough for some designers. They can go to companies such as U.K.-based ARC Cores Ltd. and Santa Clara, Calif.-based Tensilica Inc., which license embedded-microprocessor cores that are highly customizable. With these cores, it's possible to create new machine-level instructions for special purposes.
For a digital-camera processor, an instruction that speeds up JPEG image compression is valuable. For an MP3 music player, an instruction that accelerates audio decompression is equally useful. The customized designs then go to foundries for manufacturing.
Popular PC operating systems such as Windows, Mac OS and Linux are practically nonexistent in the embedded market, although Windows CE runs on some handheld computers and Linux is making inroads. Popular embedded operating systems are OS-9 (no relation to OS/2), pSOS, VelOSity, QNX, VxWorks and VRTX.
These are also called real-time operating systems, because they allow a processor to respond in a microsecond to critical events - such as a motorist stomping on a brake pedal. Despite the wide variety of such operating systems that are available, about half of all embedded-microprocessor designers write their own operating systems.
As these processors continue to become smaller, cheaper and more powerful, they will find their way into even more devices and products. Already, they're in singing greeting cards and in running shoes that measure your mileage.
Eventually, they'll be almost as common as atoms - and almost as small, thanks to nanotechnology.
Halfhill is technical editor at ARC Cores, which designs and licenses embedded-microprocessor cores.
Embedded microprocessors are computer chips used inside devices other than computers to provide added functionality, often in the areas of control and monitoring.