IAS

By : Hajer Ahmed Mohammed

ENIAC - details

• Decimal (not binary)• Its memory contained 20 accumulators of 10 digits.• 10 vacuum tubes represented each digit.• Programmed manually by switches• 18,000 vacuum tubes• 30 tons• 1500 square feet• 140 kW power consumption• 5,000 additions per second

von Neumann/Turing• Stored Program concept • Main memory storing programs and data• “Turing Machine” (Alan Turing): Given enough memory and

sufficient time the general purpose computer can compute all functions that are computable.

• 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 Computer (major components in a computer system)– Foundation for general-purpose computer

• Completed 1952

Picture of the IAS Computer

Structure of von Neumann machine

IAS - details

• 1000 x 40 bit words– 1000 storage locations of 40-bit words– Binary number– 2 x 20 bit instructions

• Set of registers (storage in CPU)– Memory Buffer Register (MBR)– Memory Address Register (MAR)– Instruction Register (IR)– Instruction Buffer Register (IBR)– Program Counter (PC)– Accumulator (AC)– Multiplier Quotient (MQ)

Structure of IAS – detailMBR

Contains a word to be stored

In memory, or is used to receive a

Word from memory.

MAR

Specifies the address in memory of the word to be written from or into MBR

IR

Contains the 8-bit opcode instruction being executed

IBR

Temporarily holds the right hand instruction from a word in memory

PC

Contains the address of the next instruction pair to be fetched from memory

IAS - details

• The IAS computer had 21 instructions which are grouped as follows:– Data Transfer: Moves data between memory and ALU

registers or between two ALU registers– Unconditional Branch: Changes the sequence of

instructions to execute repetitive operations– Conditional Branch: The branch can be made dependent on

a condition, thus, allowing decision points.– Arithmetic: Operations performed by the ALU– Address /modify: Permits addresses to be computed in the

ALU and then inserted into instructions stored in memory.

Commercial Computers

• 1947 – Eckert-Mauchly developed their own Computer Corporation

• UNIVAC I (Universal Automatic Computer)• Designed to perform mainly scientific

calculations (e.g. 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– IBM’s first stored program

computer– Scientific calculations

• 1955 - the 702– Business applications

• Lead to 700/7000 series