what is the term which differentiate the Apple A7 and Apple A8 system on a chips?
Apple A8 The Apple A8 is a 64-bit ARM-based system on a chip (SoC) designed by Apple Inc. It first appeared in the iPhone 6 and iPhone 6 Plus, which were introduced on September 9, 2014. Apple states that it has 25% more CPU performance and 50% more graphics performance while drawing only 50% of the power of its predecessor, the Apple A7.
XAP processor The XAP processor is a RISC processor architecture developed by Cambridge Consultants since 1994. XAP processors are a family of 16-bit and 32-bit cores, all of which are intended for use in an application-specific integrated circuit or ASIC chip design. XAP processors were designed for use in mixed-signal integrated circuits for sensor or wireless applications including Bluetooth, ZigBee, GPS, RFID or Near Field Communication chips. Typically these integrated circuits are used in low cost, high volume products that are battery-powered and must have low energy consumption. There are other applications where XAP processors have been used to good effect, such as wireless sensor networks and medical devices, e.g. hearing aids.