Apple A5 / Siri: why such a large processor?

Why isn’t Apple’s Siri voice recognition system designed for the iPhone 4S not available on the iPhone 4? Why is the Apple A5 processor so much bigger than the Apple A4? The first answers are starting to come through...

When Apple unveiled their Siri voice recognition system on the iPhone 4S they stated that it was only available on this device despite it being reasonably close to its predecessor the iPhone 4. The presence of a third party component was suspected as playing a role, although this couldn’t be identified when opening the smartphone.

At the same time, when looking at the Apple A5 processor present in the iPad 2 and iPhone 4S, it is surprising to see its dimensions. The A5 processor is dual core, compared to the single core in the Apple A4, but this alone doesn’t explain the size difference.

Elements about what the size difference comes from are now starting to indirectly filter through. It appears that the EarSmart technology from Audience – specialising in the treatment of voice, has been directly integrated into the Apple A5 processor whereas the iPhone 4 only has a separate voice component.

While Apple doesn’t reveal much about their processors, we know that optimisations have been made with the specific objective of updating functions to make them use as little battery power as possible.


In the Apple A5, there are more than just cores
By directly connecting to the processor, the Audience technology uses less energy and takes up less space on the motherboard. In addition, Audience indicates that their ambient noise reduction technology is more effective in this configuration than with the distinct system offered on the iPhone 4, which only works properly if the iPhone is very close to the mouth.

While the basic principles of the Siri system work perfectly well on the iPhone 4 (voice data transmission to a server which analyses the command, interaction and text data), which demonstrates that numerous developers are interested in more efficient voice recognition, which explains why Apple doesn’t offer this on the previous model.

With the system built into the iPhone 4S, it is possible to hold the device a certain distance from the face and still obtain good results. In a document which was contained within their stock market communication, Audience explains that the integration of their technology into the Apple A5 processor has allowed them to receive licensing rights from Apple, along with other manufacturers who use their technology.