1. Computer Architecture
Lecture 2
Engr. Hafiz Ali Hamza Gondal

2. Chapter 2
Computer Evolution and Performance

3. 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

4. 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

5. 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

6. Structure of von Neumann machine

7. 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

8. 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)

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

10. 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

11. 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.

12. Structure of IAS detail

13. 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.

14. 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.

15. 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.

16. Examples
Data Transfer

17. Continue…
Unconditional Branch

18. Continue…
Conditional Branch

19. Continue…
Arithmetic

20. Continue…
Address Modify

21. 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

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

23. 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.

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

25. Example of IBM

26. 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