1. The document discusses asynchronous processors, which are processors without a central clock. Asynchronous processors have no clock to coordinate data flow through the pipeline. 2. Some advantages of asynchronous processors are better power efficiency, higher performance as components can run at different speeds, and reduced electromagnetic interference. Asynchronous processors can also be easier to design. 3. The document provides a brief history of asynchronous processors and concludes that asynchronous design is competitive with synchronous design in power efficiency and performance.

1. Asynchronous
Processors: The Clock
less Future
By: Syeda Urooj
Fatima
Roll# 31

2. Clockless Logic
or
How do I make
hardware fast, power-
efficient,
less noisy, and easy-to-
design?

3. Introduction
What is asynchronous design?
Why do we want to study it?
How is data represented in an asynchronous system?

4. “Designers are realizing that
distributing a clock across even
more complicated systems is
becoming more and more difficult,
and that sooner or later it won’t
work.”
Alain Martin
Professor
Computer Science
Caltech
built first clockless
microprocessor in 1989.

5. What are Aynchronous
Processors?
• An asynchronous circuit, or self timed circuit is a
sequential digital logic circuit is not governed by a
clock circuit or global clock signal.
• Unlike conventional processor, a clockless processor
(asynchronous CPU) has no central clock to co
ordinate the progress of data through pipeline.

6. It may actually be even easier to implement
high performance devices in asynchronous
as opposed to clocked, because:
• Components can run at different speeds on asynchronous
CPU. All major components of a clocked CPU must remain
synchronized with central clock.
• A traditional CPU cannot “GO FASTER” than the expected
worst case performance of slowest stage/instruction. When
an asynchronous CPU completes an operation more
quickly than anticipated, the next stage can immediately
begin processing the results, rather than waiting for
synchronization with a entral clock.

7. Why Asynchronous
Design?
Better Power Efficiency
Only activating functional units consume power.
Inactivated parts remain in “stand-by state”
No wasteful power dissipation.
Higher Performance
No global clock.
Proceed data at appropriate rate of environment.
Do not propogate local delay globally.
Smaller chip size.
Less high frequency EMI components due to small amplitude and wide current peaks.

8. Advantages
 Works at increased speed 2.8 times.
 Low power consumption
 Twice life time.
 Less heat generated.
 Good to mobile devices.
 Less EMI Less Noise More Applications.

9. Disadvantages:
• Fewer people are trained in this style as compared to
synchronization design.
• Performance (speed) of asynchronous circuits must
be reduced in architecture that require input-
completness (More complex data path
• Incompatible with commercial EDA tools.

10. Brief History of Asynchronous Processors
 ILLIAC I and ILLIAC II(first asynchronous
designs, Uni of Illinous)
The PDP6 (Programmed Data
Processor-6) 1960 was an asynchronous
computer model.
In 2004, Epson manufactured world’s first
bendable microprocessor called ACT11, an 8-bit
asynchronous chip.

11. Conclusion:
 It is entirely practical to design a processor without a clock.
 Quality of such processors have improved with time. Some
are commercially available.
 Clock less and self timed processors open up horizons for
radical departure in main stream architectures to new and
exciting areas.
 Asynchronous design is competitive with best synchronous
design in power efficiency and is close in performance to
them.

12. References