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Processor combines high performance, low power
New microarchitecture core can change speed and voltage on the fly
By Julie Anne McNamara, Contributing Editor -- Design News, March 12, 2001
One of the more vexing challenges of designing products such as wireless Internet devices is balancing high performance with low power. The two don't usually go hand in hand. A processor that can power wireless video on a handheld computer is sure to eat up the batteries in no time.
But a new microprocessor core architecture from Intel—the XScale—can run at different voltages and thus scale through clock speeds and increase or decrease power consumption. That's the same processor core—not different versions of the design. This capability lets XScale-based processors handle requirements for both ultra-low power and high performance in devices ranging from routers and switches to wireless PDAs and smart phones.
Kick it up a notch. Designed for Intel's advanced 0.18-micron process technology, the processor core can dynamically adjust its frequency and voltage to deliver performance ranging from 1-GHz clock rates with power consumption of 1.5W to 200 MHz at 40 mW, according to the company.
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By optimizing the way a chip handles each instruction, Intel's XScale microarchitecture core can enable processors to operate more efficiently by running as fast as necessary while using as little power as possible. Key core features include dynamic voltage management and the performance-monitoring unit. |
The 1-GHz rate is fast enough to let someone watch a movie preview, listen to high-quality audio, or even take part in a videoconference from a handheld device. The varying power levels would enable such a device to run on a single AA battery.
The XScale architecture is based on Intel's StrongARM line of chips for wireless devices. Features include:
A 7-stage integer/8-stage memory super-pipelined core that enables high speed and low power. The pipeline lines up instructions to be processed, and super-pipelined processor technology lets the core scale to the higher clock speeds.
Dynamic voltage and frequency scaling that lets applications ratchet up processor performance when it's needed and conserve power when it's not.
The power-management unit, which saves power via idle, sleep, and quick wake-up modes.
A 64-bit core memory bus that allows internal accesses as fast as 4.8 Gbytes/sec.
Multimedia processing technology that uses a set of multimedia instructions similar to those used in Intel's desktop chips to enable more power-efficient multimedia processing for increasingly content-rich Internet applications.
Engineers designing products based on the XScale will be able to choose from a variety of operating systems, including Microsoft Windows CE, VxWorks and IxWorks from Wind River Systems, EPOC from Symbian, and Embedded Linux from multiple vendors.
In addition to meeting low power requirements without making significant tradeoffs in application performance, XScale will let designers base multiple designs on a single highly scalable microprocessor core that meets a wide range of performance and power requirements. This scalability enables reuse of hardware designs and software code for fast time-to-market product development.
Among it's applications:
Devices that combine personal management and calendar functions, wireless Internet access, and wireless video.
Application-specific standard products (ASSPs) for selected market segments.
The company's first XScale-based product is the 80310 I/O processor chip set, which debuted in December. It can handle I/O processing for Internet storage, networking, and embedded applications.
What do you need to know about embedded systems?
This article is one of a monthly series on "Embedded Systems and the OEM Engineer," alternately sponsored by Microchip Technology and Texas Instruments. Today's products are designed by teams—the electronics segment is part of the total design and not relegated to specialists. The lead engineer—who may or may not be an electrical engineer—is often the one who chooses a microcontroller, digital signal processor, or embedded operating system. And the trend of adding intelligence to everything from household appliances and automobiles to medical equipment and machine tools is just getting started. What do you need to know to specify the best components for your particular application? What seemingly "dumb" products are you reincarnating with embedded brains? What are your greatest challenges and frustrations? We really want to know. Please send any questions, answers, or comments to Contributing Editor Julie Anne McNamara at julie_mcnamara@email.com
PICmicros help offload high-end processors
DSPs and high-end microcontrollers and processors rarely work alone in embedded applications. An 8-bit microcontroller, such as Microchip Technology's PICmicro, often sits beside them to handle intermittent functions that are not economically smart for the high-end chip to carry out. These functions include battery management, processing keyboard input, and running displays.
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Working alongside a 32-bit microprocessor in a PDA application, a PIC MCU handles a variety of control functions. |
High-end chips can certainly perform such tasks, but they do so via the inefficient process of taking interrupts. For example, in a cell phone, every time a user pushes a button, the DSP would have to stop processing voice signals and register that action. Interrupting the DSP at a critical point could result in a skipped signal or a lost call.
As interrupt frequency goes up, system performance goes down. One solution is to use a faster chip, but chip companies charge you more money to run faster. A more cost-effective approach is spending two bucks to offload these tasks onto a PICmicro and let the high-end chip dedicate itself to high-end processing.
Cell phones, settop boxes, power supplies, notebook computers, PDAs, medical devices, and telephone switching equipment are just a few of the applications in which PICmicros work side by side with DSPs or 32-bit processors.
In cell phones, a PICmicro performs battery management and runs the keyboard and display while a DSP processes signals. The cell phone infrastructure doesn't change all that often, and the microcontroller lets designers change the device's size, keypad, display, or battery technology without touching the basic phone functions.
When the microprocessor in a settop box receives an interrupt at a certain critical time, the TV screen snows—unacceptable. In this application, a PICmicro handles the user interface and translates and formats remote-control signals for the processor. There aren't any real standards for remote-control IR protocols. Some boxes can accept more than one—especially if they are marketed worldwide. The PICmicro gets the remote-control input, figures out what task needs to be done, and sends one clear message to the processor—which can give its full attention to converting digitally compressed video of "Survivor: The Australian Outback."
To contact a Microchip Technology technical support engineer, e-mail tech.support@ microchip.com.
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