Transcript Computer Architecture

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

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Trajectory tables for weapons
Take even days for single weapon trajectory
 Started 1943 and Finished 1946
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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
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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
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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.
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STRUCTURE OF IAS
DETAIL
INSTRUCTIONS IN IAS
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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.
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CONTINUE…
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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…
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Unconditional Branch
CONTINUE…
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Conditional Branch
CONTINUE…
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Arithmetic
CONTINUE…
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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
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Faster
 More memory
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IBM
Punched-card processing equipment
 1953 - the 701
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IBM’s first stored program computer
 Scientific calculations
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1955 - the 702
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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.
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TRANSISTOR BASED COMPUTERS
Second generation machines
 NCR & RCA produced small transistor machines
 IBM 7000
 DEC - 1957
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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
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