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* Cortex designations are not in order of release date, performance, features, or power consumption. Cortex-A8 and Cortex-A9 are some of the older designs in the series; Cortex-A15 chips add hardware virtualization support. Cortex-A12, Cortex-A7, and Cortex-A5 designs followed, with varying power/performance profiles. Cortex-A53 and -A57 chips are ARMv8.
* Other companies have introduced chips with confusingly similar designations. The Apple A7 chip is not an ARM design and has nothing to do with the Cortex-A7 (or any other Cortex core); it is roughly in the same performance category as a dual-core Cortex-A53.
== big.LITTLE ==
ARM cores may be combined in compatible groups of higher-performance/high-consumption and lower-performance/lower-consumption devices. These configurations are called big.LITTLE.
Typical pairings are:
* Cortex-A15 and Cortex-A7
* Cortex-A17 and Cortex-A7
* Cortex-A57 and Cortex-A53
The advantage to big.LITTLE lies in the ability to turn off cores that are not needed. Thus, when a device such as a cellphone is performing basic background tasks (screen off), one little core may be used; when the device is performing basic tasks, a couple of little cores or one big core may be used; and when very demanding tasks are performed, several big cores (or all of the cores) may be turned on.
Balancing power vs. performance can be very difficult - for example, will it require less battery to keep a little core on constantly, or run a big core for a fraction of a second and then sleep all of the cores?
