Processor Types And Instruction SetsISASystem as WholeSystem BusCPU & MemoryA Bit about Memory (no pun intended)CPU – 2 SectionsInterface between Data and Control UnitsFETCH-EXECUTE CYCLEControl unit & Data unit (datapath) again…Datapath - > Register fileALUThe ProcessInstruction Set3 Types of InstructionsProblemsExceptionCPU typesProcessor Types And Instruction SetsBarak PerelmanCS147 Prof. LeeISA•Instruction Set Architecture•All programmer accessible hardware & instructions for that hardwareSystem as Whole•CPU (Central Processing unit) interaction with main memory (its internal memory)•Input & OutputSystem Bus•CPU connected with main memory & I/O via System Bus•CPU – generates addresses placed on Address bus•Memory – receives addresses from Address bus•THIS PROCESS NEVER REVERSEDCPU & Memory•Since CPU executes instructions, and all instructions/data stored in Memory. Instructions/data must be loaded to CPU registers, and results stored back in Memory.A Bit about Memory (no pun intended)•Memory is a collection of consecutive cells = 1 byte (8 bits)•Each cell has address/memory location•Group of cells = WORD usually 4 Bytes•Convention: WORD accessed by referencing byte with lowest byte•Computers memory is an “array” of bytesCPU – 2 Sections•1. Data Section – Registers & ALU•2. Control Section – interprets instructions and controls register transfers – executes instructions stored in main memoryInterface between Data and Control Units•Register 1: Program Counter (PC) or IP (“Instruction Pointer” in IA) – address of instruction executed•Register 2: Instruction register (IR) – fetched instruction (PC pointed) stored in IR and interpretedFETCH-EXECUTE CYCLE1. Fetch next instruc. To be exec. from memory2. Decode operation code3. Read operand(s) from main memory if any4. Exec. Instruc. and store results if any5. Go step 1Control unit & Data unit (datapath) again…•Control unit – decodes instruction after fetch, and performs specific action. Coordinates this in execution of program.•Datapath – Collection of registers (register file) , arithmetic and logic unit, and other registers.Datapath - > Register file•Register file – used like temporary “memory” during computation. •Can be many register files (depend on CPU). Each has own address (in sequence, like main memory, but with much smaller addresses –ex: 32 register file uses 5-bit address’).•Register file in CPU (much faster than system memory: ~10X’s-100X’s)ALU•Implements variety binary (2-operand) and unary (one-operand) operations (ex: add, and, not, or, multiply)The Process•Control Unit selects operands+operations according to executable instruction•The two source operands fetched from register file onto Register Source Buses to ALU•Output from ALU goes on Register Destination Bus, back to register file•Most systems include System Bus in this process (access memory and devices)Instruction Set•Collection of instructions that a processor can execute <-therefore defining the processor3 Types of Instructions1. Data – move data between CPU and memory or I/O 2. Arithmetic (logic) – arithmetic + logic operations on data3. Control – transfer control from one section to anotherProblems•Incompatibility of instruction setsSolutions•Higher-level languages recompiled for target processorException•JAVA byte code actual machine language for virtual machine. Therefore will run on any processor running JVM (Java Virtual Machine)CPU types•IBM PC (or compatible) use instruction set 80x86 CPU (where ‘x’ replaced w/digit of version. Example: 80586 aka Pentium processor) (*also need to consider differences in in operating systems and I/O)•Sun Microsystem
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