Basic logical operations Operation Mechanism Through the combination of circuits that perform these three operations, a wide range of logical circuits is implemented. Logical product operation (AND operation) Logical sum operation (OR operation) Negation operation (NOT operation) Basic logical operations Logical sum (OR) Logical product (AND) Logical operationsOperation symbols Negation (NOT) Exclusive logical sum (EOR) Negative logical sum (NOR) Negative logical product (NAND) ^ ∙ V + ¯ ¬ A Logical Circuits Basic Circuits and their Combination AND circuit OR circuit NOT circuit EOR circuit NOR circuit NAND circuit Combinational Circuit Identity circuitAddition circuit Half adder circuit Full adder circuit Sequential Circuit Flip-flop circuit

AND circuit of a switch and a light bulb AND circuit Basic logical circuits Operation Mechanism Truth Table ABA AND B Venn Diagram A^B (or A∙B) switch A switch B switch Aswitch B open (0) close (1) open (0) close (1) A: 0 B: 0 A ^ B = 0 A: 0 B: 1 A ^ B = 0 A: 1 B: 0 A ^ B = 0 A: 1 B: 1 A ^ B = 1 A B Y MIL –STD US Military standard AND symbol

OR circuit of a switch and a light bulb OR circuit Basic logical circuits Operation Mechanism Truth Table ABA OR B Venn Diagram A ν B (or A+B) AB A B Y MIL –STD US Military standard OR symbol

NOT circuit of a switch and a light bulb NOT circuit Basic logical circuits Operation Mechanism Truth Table ANOT A A Venn Diagram ¬ A A A Y MIL –STD US Military standard NOT symbol

EOR, NOR & NAND circuits Combination of the basic circuits Operation Mechanism Truth Tables ABA EOR B ABA NOR B ABA NAND B A B Y MIL –STD US Military standard EOR symbol A B Y NOR symbol A B Y NAND symbol Exclusive logical sum operation circuit Negative logical sum operation circuit Negative logical product operation circuit

Addition circuits Combination of the basic circuits Operation Mechanism Truth Table InputOutput ABCD Half-adder circuit Addition of two 1-digit nos. a + b ── c d Full-adder circuit a c' EOR circuit AND circuit EOR circuit AND circuit OR circuit b Result d Carry e a b EOR circuit AND circuit Result d Carry c InputOutput c’abed c' a + b ── e d

Sequential circuit Combination of the basic circuits Operation Mechanism Sequential circuit a circuit in which the output is established according to the current input and the status preserved (past input). status changes with time composed of a flip-flop circuit and is used in registers, etc. NOR circuit

2.2.4 Multi-Processor Multi-processor systems are introduced to improve the performance and reliability of the system. Multiple processors are in parallel with each processor having a dedicated function. When failure occurs, the processor will do a switch and the remaining processors will distribute the load among themselves.

Symmetric Multi-Processor Multi-Processor Memory is shared among all the processors executing the same OS. Competition for the use of memory among the processors since the memory common to all. A large number of processors cannot be connected. Message passing distributed memory multi processor systems - systems where each processor has its own private block memory. - a high speed I/O port is used to transfer the data between the different blocks.

Array Processor Multi-Processor The sub units’ acts are in a queue passing the result to the next unit after it has finished its part (vector processing) Mostly used in: Supercomputers High speed scientific computing Large scale or dedicated mathematical processors

Parallel Multi-Processor Multiple processors cooperate with multiple tasks being performed to execute one job. SISD (Single Instruction Single Data Stream) One Instruction stream operating on a single data element and is not parallel. SIMD (Single Instruction Multiple Data Stream) Each instruction may operate on more than one data element and is synchronous. Parallel SIMD The same instruction is executed by all processors operating on different sets of data MIMD (Multiple Instruction Multiple Data Stream) Each instruction has its own instruction stream and acts on its own data stream independent of other processors.

MIPS (Million Instructions per Second) Processor performance Indicates, in million units, the number of instructions that can be executed in one second. The higher the number of instructions that can be executed, the higher the value. Mainly used to indicate the performance of processors of high-end mainframe computers. However, it is meaningless to use this index to compare processors of different types of machines that execute different instruction contents.

Clock Processor performance A processor has an internal clock to set the pace in which the micro-instructions, which are basic operations, are executed, Uses a quartz crystal oscillator that pulses in regular intervals when electric current passes through. The time taken for this oscillator to pulse once (one cycle) is called clock. The basic operations of the processor are performed according to this clock. The number of clocks vary according to the instruction. Clock Frequency - clock reciprocal number - used as an index to measure the performance of a personal computer.

CPI (Cycles per Instruction) Processor performance A CPI is the number of clocks required to execute one instruction. This index indirectly indicates the execution time of one instruction.