Cortex-A8处理器简介
特点：
Cortex-A8是一款成功的ARM内核。
（1）支持ARM体系结构的v7-A指令集。
（2）使用流水线技术。
（3）MMU（Memory
Management Unit）。
（4）动态和静态的电源管理方案（IEM：Intelligent Energy Management）
From：Cortex-A8 TRM
【The processor implements the ARMv7-A architecture. This includes:
• the 32-bit ARM instruction set
• the 16-bit and 32-bit Thumb-2 instruction set
• the ThumbEE instruction set
• the Security Extensions architecture
• the Advanced SIMD architecture.】
延伸（from：https://en.wikipedia.org/wiki/ARM_architecture）
Jazelle
Jazelle DBX (Direct Bytecode eXecution) is a technique that allows Java Bytecode to be executed directly in the ARM architecture as a third execution state (and instruction set) alongside the existing ARM and Thumb-mode. Support for this state is signified by the "J" in the ARMv5TEJ architecture, and in ARM9EJ-S and ARM7EJ-S core names.
Thumb
To improve compiled code-density, processors since the ARM7TDMI (released in 1994[70]) have featured the Thumb instruction set, which have their own state. (The "T" in "TDMI" indicates the Thumb feature.) When in this state, the processor executes the Thumb instruction set, a compact 16-bit encoding for a subset of the ARM instruction set.
Thumb-2
Thumb-2 technology was introduced in the ARM1156 core, announced in 2003. Thumb-2 extends the limited 16-bit instruction set of Thumb with additional 32-bit instructions to give the instruction set more breadth, thus producing a variable-length instruction set. A stated aim for Thumb-2 was to achieve code density similar to Thumb with performance similar to the ARM instruction set on 32-bit memory.
Thumb Execution Environment (ThumbEE)
ThumbEE (erroneously called Thumb-2EE in some ARM documentation), marketed as Jazelle RCT (Runtime Compilation Target), was announced in 2005, first appearing in the Cortex-A8 processor. ThumbEE is a fourth instruction set state, making small changes to the Thumb-2 extended instruction set. These changes make the instruction set particularly suited to code generated at runtime (e.g. by JIT compilation) in managed Execution Environments. ThumbEE is a target for languages such as Java, C#, Perl, and Python, and allows JIT compilers to output smaller compiled code without impacting performance.