Context of the great gatsby

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168 420 Computer ArchitectureChapter 11CPU Structureand FunctionCPU Structure]CPU must:\Fetch instructions\Interpret instructions\Fetch data\Process data\Write dataRegisters]CPU must have some working space (temporarystorage)]Called registers]Number and function vary between processordesigns]One of the major design decisions]Top level of memory hierarchyUser Visible Registers]General Purpose]Data]Address]Condition CodesGeneral Purpose Registers (1)]May be true general purpose]May be restricted]May be used for data or addressing]Data\Accumulator]Addressing\SegmentGeneral Purpose Registers (2)]Make them general purpose\Increase flexibility and programmer options\Increase instruction size & complexity]Make them specialized\Smaller (faster) instructions\Less flexibility
How Many GP Registers?]Between 8 - 32]Fewer = more memory references]More does not reduce memory references andtakes up processor real estate]See also RISCHow big?]Large enough to hold full address]Large enough to hold full word]Often possible to combine two data registers\C programming\double int a;\long int a;Condition Code Registers]Sets of individual bits\e.g. result of last operation was zero]Can be read (implicitly) by programs\e.g. Jump if zero]Can not (usually) be set by programsControl & Status Registers]Program Counter]Instruction Decoding Register]Memory Address Register]Memory Buffer Register]Revision: what do these all do?Program Status Word]A set of bits]Includes Condition Codes]Sign of last result]Zero]Carry]Equal]Overflow]Interrupt enable/disable]SupervisorSupervisor Mode]Intel ring zero]Kernel mode]Allows privileged instructions to execute]Used by operating system]Not available to user programs