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Chipmakers look for new ways to take PC's temperature

Posted: 17 Sep 2003 ?? ?Print Version ?Bookmark and Share

Keywords:national semiconductor? pc? computer?

As processors get hotter and the desktop systems they go into get smaller and more complex, some engineers believe it's time for a new way to track the PC's internals.

National Semiconductor Corp. and at least one other company have submitted competing proposals for revamping the way that PCs monitor key internal health data, such as component temperatures. The ad hoc task force studying distributed management is reviewing the proposals now and could issue a standard in less than a year.

Not waiting for the standards process, National has started sampling two SuperI/O chips and two temperature sensors that use an approach based on a new sensor bus that the company has defined.

The National architecture essentially replaces today's practice of sending analog data down relatively long motherboard traces over the two-wire Systems Management Bus (SMBus) to a Heceta ASIC, typically to monitor CPU temperature. Instead, National advocates a single-wire SensorPath bus that could connect as many as seven temperature, voltage and other sensor devices sending digital data back to a SuperI/O chip.

The National approach could provide greater accuracy of readings and finer-grained control of system-level temperature and fan speeds, said John Hull, director of marketing for National's advanced PC division, and it would cost less to implement.

Hull noted that the upcoming Prescott version of Intel's Pentium 4 processor dissipates up to 100 watts, while Intel is promoting a small form factor initiative for desktops and OEMs are trying to reduce the number of fans in their home systems to one or none.

"This is a big problem on the PC motherboard these days," Hull said. "And there's too much stuff connected to the SMBus today. That can be an issue at boot-up time."

National's SensorPath proposal comes as the company is jettisoning the X86 processor group it acquired from Cyrix Corp. and a separate cellphone baseband group to focus on analog products such as sensors. The company hopes its SensorPath approach lets PC makers monitor more functions inside a system at less cost while still buying more National parts.

"Given the breadth of IP National has in this area, we're in a good position to help set a standard," said Hull.

Kevin Cline, chairman of a BIOS-level working group at the distributed-management task force, said, "The problem statement [presented by National and others] has been ratified, but we are still looking at different implementations."

The task force is reviewing at least two full-blown proposals now and could produce a standard in about six months providing contention is low and the proposals are complete, Cline said.

Meanwhile National has started sampling four products that ride its SensorPath.

The PC8374L is a desktop SuperI/O chip that supports serial, parallel, floppy, and PS/2 keyboard interfaces. It will be available in quantity in the first quarter of next year at $2.35 each in 1,000s. The server-class PC87427 supports up to eight fans and two copies of BIOS for redundancy. It will be in production in October for $9.75 each in 1,000s. Each comes in a 128-pin quad flat pack and is made in 180nm technology.

National's LM95010 is an eight-pin measurement-system operating procedure temperature sensor that supports two remote diode temperature inputs; it will be available in November for $1 each in 1,000s. The LM96010 temperature sensor has four hardware-programmable addresses, fits in a 14-pin TSSOP and will be available in the first quarter of '04 at $1.50 each in 1,000s.

- Rick Merritt

EE Times

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