EEPW论坛

谁能形象地讲解一下850/860里的这几个汇编指令

eieio;

sync

isync

能讲一下手册上所说的:(大概翻译一下）

5.2.2.3 Synchronization The synchronization described in this section refers to the state of the processor that is performing the synchronization. 5.2.2.3.1 Context Synchronization The System Call (sc) and Return from Interrupt (rfi) instructions perform context synchronization by allowing previously issued instructions to complete before performing a change in context. Execution of one of these instructions ensures the following: No higher priority exception exists (sc). All previous instructions have completed to a point where they can no longer cause an exception. Previous instructions complete execution in the context (privilege, protection, and address translation) under which they were issued. The instructions following the sc or rfi instruction execute in the context established by these instructions.

5.2.2.3.2 Execution Synchronization An instruction is execution synchronizing if all previously initiated instructions appear to have completed before the instruction is initiated or, in the case of the Synchronize (sync) and Instruction Synchronize (isync) instructions, before the instruction completes. For example, the Move to Machine State Register (mtmsr) instruction is execution synchronizing. It ensures that all preceding instructions have completed execution and will not cause an exception before the instruction executes, but does not ensure subsequent instructions execute in the newly established environment. For example, if the mtmsr sets the MSR[PR] bit, unless an isync immediately follows the mtmsr instruction, a privileged instruction could be executed or privileged access could be performed without causing an exception even though the MSR[PR] bit indicates user mode.