| 摘要 |
<p>In a data processing system employing microcode techniques, complex sequences of microinstructions can be initiated by application of a single macroinstruction. These complex sequences of microinstructions are typically noninterruptible and therefore the execution of a macroinstruction is atomic (i.e., executed as a single entity). Data processing systems that do not employ microcode typically have simpler macroinstruction sets that do not provide for a similar atomicity for complex instruction sequences. In order to obtain the same atomicity of instruction execution and to provide a nonmicrocoded data processing system with the capability to execute complex instruction sequences as a atomic operation, the nonmicrocoded data processing system is provided with a third mode, in addition to the (nonprivileged) user mode and the (privileged) kernel mode, of operation that permits the execution of instruction sequences with interrupting events disabled and certain functions and apparatus enabled to facilitate instruction sequence execution.</p> |
