The Apple A5 system-on-a-chip (SoC) was first introduced alongside the iPad 2 and later became the heart of the iPhone 4s, and iPad mini. Reportedly based on ARM's Cortex A9 central processing unit with Imagination's PowerVR SGX 543MP2 graphics processing unit, Apple will only say it provides 2x the computing power and 7x the graphics power of iPhone 4. This lets it power everything from AirPlay Mirroring to the Siri virtual assistant.
Doing bigger things isn't the only point, however. Doing more smaller things faster makes a difference as well. Launching apps, rendering and scrolling through web pages, playing games -- all these things are palpably faster. Near-instant, in fact. You'll feel it right away, and if you ever go back to an older iPhone or smartphone, you'll miss it immediately.
Interestingly, Apple's stuck with the same 512MB of RAM for the A5. While competing phones are sporting 1GB these days, Apple seems to believe they don't need more RAM for better performance, or perhaps don't need the potential tradeoff in power consumption.
the iPad 3 launched with a souped up version of the Apple A5 dubbed the Apple A5X. While still a dual-core CPU (Central Processing Unit), the Apple A5X has a quad-core GPU (Graphics Processing Unit), powered as usual by Imagination's PowerVR technology, and a full 1GB of RAM.
In practice that may sound like it should lead to a faster new iPad. However, a lot of that power is directed into supporting the new Retina display. 4 times as many pixels means 4 times as many pixels to buffer and push around, after all. So, instead of being faster, it's working harder to maintain the same speed.
And that turned out to be sub-optimal. Especially for games.
Apple A5 and the Apple TV
The Apple TV is currently powered by a single core version of the Apple A5 processor.
Apple A5 and A5X: The bottom line
The Apple A5 and Apple A5X were succeeded by the Apple A6 and A6X