Why Siri doesn't like older iPhones

The folks at iFixit believe Siri's lack of support for older iPhones is due to a change in the proximity sensor in the iPhone 4S over previous models. But there are other theories out there.

Even Siri won't reveal why she doesn't support older iPhones.
Even Siri won't reveal why she doesn't support older iPhones. Screenshot by Lance Whitney/CNET

iPhone 4S users have been able to enjoy conversations with Siri. But owners of older iPhones have no Siri to talk to. Why?

Tearing down the iPhone 4S, the gurus at iFixit believe that Siri's absence on older phones is connected to changes in the proximity sensor used in the new iPhone.

The proximity sensor judges when your face is near the phone so it can dim the display and disable the keyboard. In past model iPhones, it turns on only during a call and then turn offs when the call is completed.

But Siri also makes use of the proximity sensor since there's a "raise-to-speak" option that activates the voice assistant when you bring the phone to your face.

To enable this feature, the proximity sensor in the new phone is now active all the time, not just during a call, says iFixit. This means that the sensor's infrared LED is constantly shining, though it's undetectable except through certain digital cameras, which is how iFixit found and recorded it.

This finding initially led others, including 9to5Mac readers, to assume that iFixit was pinning the blame on an actual hardware change in the sensor for the iPhone, which prompted iFixit to respond with the following clarification:

"The IR LED definitely appears to be different on the 4S when compared to the iPhone 4, but we don't think that the hardware change is causing the light to be continuously lit. That functionality is built into the software system, since it's the software that tells the light when to turn on, and when to turn off."

Still, some of the commenters on 9to5Mac seem dubious that the proximity sensor is the only reason why Siri won't work on older iPhones. The raise-to-speak option is not necessary to use Siri, as several pointed out. Apple lets iPhone 4S users turn off that option, in which case Siri can be activated just by holding down the home button.

Some reports have claimed that Siri requires the power of the dual-core A5 chip found in the iPhone 4S. But that same chip powers the iPad 2. Others have pointed to the quality of the microphone on the iPhone 4S as a factor.

I even asked Siri why she doesn't support older iPhones, but she played dumb, instead displaying a page of definitions from Wolfram Alpha.

Whatever the reason, the future of Siri on older iPhones remains unclear. One recent report claimed that Apple was testing the feature on the iPhone 4 and other models. But another report said that Apple has no plans to support Siri on anything but the iPhone 4S .

Some developers and hackers have been striving to get the voice assistant to talk on older iPhone models as well other Apple devices.

Hacker Steven Troughton-Smith said that he was able to get Siri to work on an iPhone 4 and and iPod Touch , though with some limitations. Troughton-Smith also managed to coax Siri onto an iPhone 3GS but he conceded that the performance was not good.

Apple did not immediately respond to a request for comment on just why Siri isn't supported on older iPhones.

 

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