Instruction and instruction
The computer system is composed of two parts, hardware and software. It refers to the actual hardware device by the central processor, memory and peripheral devices thereof. A variety of software systems for computer and user written program. A program of computer instructions by the sequence.
Instruction is the smallest unit of the computer running the function, the command is a command to run the computer hardware, a bit string composed of a plurality of binary bits, computer hardware and can be performed directly identify the message body. Instructions should indicate completion instruction operation, and clearly the operation target.
A computer all the instructions provided by the computer system configuration instructions. Instructions for programming staff inform the computer to perform a basic operation, processing, multiple instructions can be composed of a program, it is expected to complete a task.
Position instruction in the computer
You can analyze and look at the basic components of a computer system from six levels.
Instruction layer is between the hardware and software systems. Is a hardware interface between software components, have a significant impact on the two parts.
Hardware systems for functions implemented for each instruction to address the convergence of the relationship between the command.
Software consists of many instructions organized according to certain rules of composition, the completion of certain data operations or transaction processing.
Pros and cons of instruction is a key factor in whether a computer system successful.
Instruction functional classification
- Operation instruction data
arithmetic operations, logic operations - Data transfer instruction
between registers, main memory / register - Input / output instruction
to the input / output port of the data transmission - Control command
transfer instruction, subroutine call / return instructions - Other instructions
off, on / off interrupt, empty operation, privileges, set the condition code
Instruction format
Instruction format: opcode and instruction word operand address bit allocation scheme
opcode: instruction operation function specified in this section, there is a determination for each instruction opcode.
Operand address: operand storage address, and sometimes operand itself.
Instruction word: the complete binary representation of an instruction.
Instruction word length: digit binary code instruction word.
Machine word: the number of bits of binary data can deal directly with the computer.
Instruction word (multiple bytes): 0.5, 1, ... a machine word.
Fixed-length instruction word structure ---------------------- variable length instruction word structure
fixed-length opcode -------------- -------------- extended opcode
Addressing
Addressing mode (also called addressing mode) refers to a method of determining section instruction operand address and the next instruction address to be executed.
Different computer systems using different numbers and addressing functions, the complexity of its implementation and running properties vary. Some computer addressing less, while using a variety of addressing modes have a computer.
Typically it requires a dedicated address field in the instruction for each operand, source or destination address is used to represent data. Address of the operand in the given instruction address form is referred to. Use in the form of address information according to certain rules or calculated from a value obtained by the read operation, the address is the actual data. In the operand field may indicate instructions:
- The accumulator computing unit ID name or special purpose registers.
- Input / output instructions used in the I / O device into a port address.
- Address memory cells in a memory (or I / O device).
Computer performance evaluation
- Throughput
quantity per unit of time to complete the task - Response time
to complete the task in time - The indicators measure the performance
MIPS
CPI
the CPU Time
the CPU Clock - Comprehensive test program (test bed)
