The document discusses bottlenecks in high-speed CPU design, including that clock speeds cannot increase beyond a limit due to the speed of light and heat dissipation problems. It also discusses how reducing supply voltage and adjusting clock speeds dynamically can help conserve power and manage heat in CPUs. The document lists applications that require intensive computing such as weather forecasting, molecular modeling, and bioinformatics. It notes that supercomputers use parallel processing to achieve high speeds for such applications, with the fastest performing over 33 petaflops. The document also summarizes Flynn's taxonomy of computer architectures.

1. General Aspects of Computer Organization
(Lecture-5)
R S Ananda Murthy
Associate Professor and Head
Department of Electrical & Electronics Engineering,
Sri Jayachamarajendra College of Engineering,
Mysore 570 006
R S Ananda Murthy General Aspects of Computer Organization

2. Bottlenecks in High Speed CPU Design
Speed of light is limited to 20 cm/nanosecond in copper
wire or optical fibre.
Faster chips produce more heat whose dissipation is a
very big problem.
CPU clock speeds cannot be increased beyond a limit
because of the reasons mentioned above.
R S Ananda Murthy General Aspects of Computer Organization

3. Supply Voltage and Clock Affect Power Loss in CPU
Present trend is to reduce the operating voltage of the
CPU to reduce the power loss.
Typical CPU voltage now-a-days is in the range 2.8 V to
3.5 V.
Often a switching voltage regulator converts from 5 V or
12 V or some other voltage to whatever voltage is required
by the CPU.
To conserve power and manage heat, many laptop and
desktop processors have a power management feature
that allows software (usually the operating system) to
adjust the clock speed and core voltage dynamically.
In power saving mode the CPU operates at lower voltage
and clock frequency.
R S Ananda Murthy General Aspects of Computer Organization

4. Applications Requiring Intensive Computing
Weather forecasting and climate research.
Oil and gas exploration.
Fluid flow analysis.
Molecular modeling.
Computations in the domain of quantum mechanics.
Simulation of astronomical events.
Finite element analysis in structural design.
Simulation of very large physical systems like world
economy.
Computer Aided Design.
Bioinformatics
R S Ananda Murthy General Aspects of Computer Organization

5. Supercomputers are Parallel Computers
In computationally intensive applications listed earlier,
typically, the same calculations are performed on large
sets of data.
In such applications, only pipelining and superscalar
architecture will not result in sufficient speed of
computation.
Then parallel computing is the only approach to increase
the computational speed.
Speed of supercomputers is expressed in FLoating Point
Operations Per Second (FLOPS).
As of August 2015, Milky Way-2, a supercomputer
developed by China’s National University of Defense
Technology, is the world’s fastest with a performance of
33.86 petaflop/s (1 peta=1015).
R S Ananda Murthy General Aspects of Computer Organization

6. Flynn’s Classification of Digital Computers
Professor M. J. Flynn of Stanford University, proposed the
following classification of digital computers in 1966 –
Single Instruction Single Data (SISD) stream computers.
Eg. Desktops and laptops.
Single Instruction Multiple Data (SIMD) stream computers.
Eg. GPUs used in high speed graphics cards.
Multiple Instruction Single Data (MISD) stream computers.
Eg. Computers used in fault-tolerant flight control systems
used in aeroplanes, missiles and space vehicles.
Multiple Instruction Multiple Data (MIMD) stream
computers. Eg. Almost all supercomputers.
R S Ananda Murthy General Aspects of Computer Organization

7. SISD and MISD Architecture
Source: https://en.wikipedia.org/wiki/Flynn’s_taxonomy
Each Processing Unit (PU) will be typically having its own
ALU with input and output registers.
R S Ananda Murthy General Aspects of Computer Organization

8. SIMD and MIMD Architecture
Source: https://en.wikipedia.org/wiki/Flynn’s_taxonomy
R S Ananda Murthy General Aspects of Computer Organization

9. License
This work is licensed under a
Creative Commons Attribution 4.0 International License.
R S Ananda Murthy General Aspects of Computer Organization