Apple's CPU undervolting patent has numerous problems -- it involves a law of nature, it's vague, and it deals with a large volume of prior art. It's kind of like trying to patent "A System for Selectively Staying Home From Work to Avoid Driving in Too Deep Snow and Having an Accident".  (Source: Free Foto)
We look at one of Apple's more controversial patents

On Tuesday Apple filed suit against HTC, makers of the HTC Hero and Nexus One, Android phones.  Some say the suits are misdirection, other say it's a sign of concern from Apple that Android is gaining momentum, regardless they seem rather strange given some of the patents.

It's definitely worth taking a quick look at at least one of these patents and why there's questions about it.

One of the patents that is drawing the most attention is a patent involved in the case that describes cell phone CPU undervolting, entitled, "US Patent 6920574 - Conserving power by reducing voltage supplied to an instruction-processing portion of a processor".  The patent was issued to Apple in 2005 and states that Apple has invented the concept of an interrupt that tells a processor to not only cut the clock to a part of the CPU, but cut the voltage as well.

Describes Apple:
One embodiment of the present invention provides a system that facilitates reducing static power consumption of a processor. During operation, the system receives a signal indicating that instruction execution within the processor is to be temporarily halted. In response to this signal, the system halts an instruction-processing portion of the processor, and reduces the voltage supplied to the instruction-processing portion of the processor. Full voltage is maintained to a remaining portion of the processor, so that the remaining portion of the processor can continue to operate while the instruction-processing portion of the processor is in reduced power mode.
There's multiple problems there.  First, the patent is overly vague.  Of course this is true of many patents, but its definitely true in this case.  Apple's description of the CPU in question and the interrupts itself are exercises in generality discussing many well known concepts (processor architecture, interrupts, power management), leaving the reader unclear of exactly what Apple has actually "invented".

Second, the patent revolves around a law of nature, power = voltage times current (P=VI), and thus its patent worthiness is questionable.  On a most basic level the patent states: If I want to make a change to the result of a commonly known formula dictating natural phenomena I send a signal to change one of the variables.

There's a bit more to it than that -- talk of maintaining power to the cache to maintain state information, but on a basic level the patent goes back to (P=VI).  So perhaps a better analogy is: If I want to make a change to the result of a commonly known formula of nature I send a signal to change one of the variables, but when I get the signal I don't change the variable for another part of my system, which I don't want to change the formula result for.

To give an analogy that's about like a hypothetical patent on "A System for Selectively Staying Home From Work to Avoid Driving in Too Deep Snow and Having an Accident".  The system would be quite useful for northern states, after all.  It might involve the following:
1.  A system that monitors the outdoor environment for changes in the weather (your eyes and internet connection).
2.  When it begins to snow heavily, send a signal that you will not be driving (call in to work).
3.  Do some short range driving (but not to work) to maintain the essential supplies (maintain your cache of supplies, get it?).
Finally, there's the problem of prior art.  Interrupts have been around for decades as has the concept of undervolting/overvolting.  Power-off interrupts (reducing the voltage) have existed for decades as well, so it's questionable that the scheme Apple describes hadn't been done before 2005.

Some of Apple's other patents involved in the HTC case have similar issues.  Patent law is a quirky field, though, and the U.S. patent system obviously has a very inconsistent track record of late.  HTC has little intellectual property that it can use to fight back against Apple with (versus a giant like Google or Microsoft) and also less money, given the razor-thin margins on its handset hardware.  As a result, Apple does stand a fighting shot at kill HTC's sales in the case, even if its patents aren't as strong, merely because it has more resources.

"It seems as though my state-funded math degree has failed me. Let the lashings commence." -- DailyTech Editor-in-Chief Kristopher Kubicki

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