Computer Architecture Lecture 2 Engr. Hafiz Ali Hamza Gondal

Chapter 2 Computer Evolution and Performance

ENIAC - background Electronic Numerical Integrator And Computer Eckert and Mauchly at University of Pennsylvania The Army’s Ballistics Research Laboratory (BRL) More than 200 people and calculators to find Trajectory tables for weapons Take even days for single weapon trajectory Started 1943 and Finished 1946 Too late for war effort Used until 1955

ENIAC characteristics Decimal (not binary) 20 accumulators of 10 digits Programmed manually by switches 18,000 vacuum tubes 30 tons 15,000 square feet 140 kW power consumption 5,000 additions per second

von Neumann/Turing Stored Program concept Main memory storing programs and data ALU operating on binary data Control unit interpreting instructions from memory and executing Input and output equipment operated by control unit Princeton Institute for Advanced Studies IAS Completed 1952

Structure of von Neumann machine

Components A main memory, which stores both data and instructions An arithmetic and logic unit (ALU) capable of operating on binary data A control unit, which interprets the instructions in memory and causes them to be executed Input and output (I/O) equipment operated by the control unit

Neumann’s earlier proposal, This structure was outlined in von Neumann’s earlier proposal 1st First: Because the device is primarily a computer (CA) 2nd The logical control of the device (CC) 3rd Complicated Operations (M) 4th and 5th The device must have organs to transfer information from/to Outside medium device (R) Input (I) Output(O)

IAS (Institute of Advanced studies) 1000 locations of 40 bits Binary number 2 x 20 bit instructions Signed bit representation

Registers Memory buffer register (MBR): Contains a word to be stored in memory or sent to the I/O unit, or is used to receive a word from memory or from the I/O unit. Memory address register (MAR): Specifies the address in memory of the word to be written from or read into the MBR. Instruction register (IR): Contains the 8-bit opcode instruction being executed

Continue… Instruction buffer register (IBR): Employed to hold temporarily the right hand instruction from a word in memory. Program counter (PC): Contains the address of the next instruction-pair to be fetched from memory. Accumulator (AC) and multiplier quotient (MQ): Employed to hold temporarily operands and results of ALU operations. For example, the result of multiplying two 40-bit numbers is an 80-bit number the most significant 40 bits are stored in the AC and the least significant in the MQ.

Structure of IAS detail

Instructions in IAS The IAS computer had a total of 21 instructions, which are listed in Table 2.1.These can be grouped as follows: Data transfer: Move data between memory and ALU registers or between two ALU registers Arithmetic: Operations performed by the ALU.

Continue… Unconditional branch: Normally, the control unit executes instructions in sequence from memory. This sequence can be changed by a branch instruction, which facilitates repetitive operations. Conditional branch: The branch can be made dependent on a condition, thus allowing decision points.

Continue… Address modify: Permits addresses to be computed in the ALU and then inserted into instructions stored in memory. This allows a program considerable addressing flexibility.

Examples Data Transfer

Continue… Unconditional Branch

Continue… Conditional Branch

Continue… Arithmetic

Continue… Address Modify

Commercial Computers 1947 - Eckert-Mauchly Computer Corporation UNIVAC I (Universal Automatic Computer) US Bureau of Census 1950 calculations Became part of Sperry-Rand Corporation Late 1950s - UNIVAC II Faster More memory

IBM Punched-card processing equipment 1953 - the 701 1955 - the 702 IBM’s first stored program computer Scientific calculations 1955 - the 702 Business applications Lead to 700/7000 series

Transistors Replaced vacuum tubes Smaller Cheaper Less heat dissipation Solid State device Made from Silicon (Sand) Invented 1947 at Bell Labs byWilliam Shockley et al.

Transistor Based Computers Second generation machines NCR & RCA produced small transistor machines IBM 7000 DEC - 1957 Produced PDP-1

Example of IBM

Microelectronics Literally - “small electronics” A computer is made up of gates, memory cells and interconnections These can be manufactured on a semiconductor e.g. silicon wafer