Chapter 4 Key Terms ITE 221

Execution cycle

addition, subtraction or another data transformation takes place, and the data output is stored.

Logical Shift instruction

can extract a single bit from a bit string.

Exclusive XOR instruction

generates the value of true if one of the data inputs are true. Generates the value of false if both data inputs are true or if both data inputs are false.

Generalpurpose registers

used only by the currently executing program.

Instruction

a command to the CPU to perform one of its primitive processing functions on specific data inputs. An instruction is made up of an opcode and one or more operands.

Conductivity

electrical current is the flow of electrons from one place or device to another through conductors.

Special

purpose registers used by CPU for specific purposes.

Branch operations

a branch instruction causes the processor to depart from sequential instruction order.

Opcode

a unique binary number of the instruction.

Conditional Branch

occurs only if a specified condition is met, such as the equivalence of two numeric variables.

Clock rate

the frequency at which the system clock generates timing pulses.

Instruction pointer (program counter)

stores the address of the instruction retrieved by the control unit. The instruction pointer is incremented by the control unit either during or immediately after each fetch cycle.

Halt operation

suspends the normal flow of instruction execution in the current programs.

Program Status Word

contains data that describes the status of the CPU and the currently executing program.

Shift instruction

bit strings can be shifted to the right or left, the number of positions shifted may be greater than one.

GigaHertz

billions of cycles per second.

Fetch cycle

data inputs are prepared for transformation into data outputs. Instruction moved from primary storage to the control unit.

Resistance

the loss of electrical power that occurs within a conductor.

Inclusive OR instruction

generates the value true if either or both data inputs are true. Generates the value of false if both data inputs are false.

Clock cycle

each tick of the clock starts a new clock cycle.

Hertz

corresponds to one clock cycle per second.

Multiprocessing

any CPU architecture in which duplicate CPUs or processor stages can execute in parallel.

Pipelining

a method of organizing CPU circuitry to enable multiple instructions to be in different stages of execution at the same time.

Load operation

is a data transfer from main memory into a register.

Wait state

each clock cycle that the CPU spends waiting for a slower device.

ADD instruction

accepts two numeric inputs and produces their arithmetic sum.

Millions of Floating point Operations Per Second (MFLOPS)

CPU performance when manipulating single precision floating point number.

System Clock

a digital clock that generates timing pulses, or signals, and transmits the pulses to other devices within the computer.

NOT instruction

transforms the Boolean value true into false.

Arithmetic Shift instruction

performs multiplication or division. Shifting to the left by one bit multiplies the value by two. Shifting to the right by one bit divides the value by two.

Variable length instruction

the amount by which the instruction pointer is incremented after the fetch is the length of the most recently fetched instruction.

Microprocessor

a microchip that contains all the circuits and connections that implement a CPU.

AND instruction

generates the result of true if both of its data inputs are true. Generates the result of false if one or both of its data inputs are false.

Sequence control operations

alter the flow of instruction execution in a program.

Branch prediction

the CPU guesses whether a branch condition will be true or false based on past experience.

Instruction format

a template that specifies the number of operands and the position and length of the op code and operands.

Reduced Instruction Set Computing (RISC)

a processor without complex instructions from the instruction set. The processor avoids instructions that combine data transformation and data movement operations.

Instruction Set

the collection of instructions that a CPU can process.

Benchmark

a measure of CPU or computer system performance when executing one or more specific tasks.

Integrated Circuit

several transistors and their interconnections are placed on a single chip.

MOVE instruction

copies data bits to storage locations.

Heat sink

an object specifically designed to absorb hear and rapidly dissipate the heat via air or water movement.

Gate

a circuit that can perform a processing function on an individual binary electrical signal or bit. Processing functions performed by gates include the logical functions AND, OR, XOR and NOT.

Fixed length instruction

the amount by which the instruction pointer must be incremented after each fetch is a constant.

Millions of Instructions Per Second (MIPS)

measure CPU performance when manipulating single precision integers.

Unconditional Branch

the processor always departs from the normal execution sequence.

Word

a unit of data that contains a fixed number of bytes or bits. A CPU with a large word size can process faster than a CPU with a smaller word size.

Instruction register

a specialpurpose register that

Complex Instruction Set Computing (CISC)

processor architecture that uses complex instructions that embed many primitive processing operations, in contrast to RISC.

Operand

input values for the instruction.

Store operation

is a data transfer from a register into primary storage.