1. GREENDROID: EXPLORING THE NEXT
EVOLUTION IN SMARTPHONE APPLICATION
PROCESSOR

2. CONTENTS
 Technology
 Problem Statement.
 Basic definition involved.
 Proposed Schemes.
 Design Goals.
 Architectures.
 Methodology.
 Result.
 Future Enhancement.
 Conclusion.

3. TECHNOLOGY
This study is mainly for smart phone application
processor. Smartphone applications' energy efficiency is vital, but many
Android applications suffer from serious energy inefficiency problems . So
Greendroid is discussed to eradicate this problem and make the processors
energy efficient.

4. PROBLEMS IN THE SMARTPHONE PROCESSOR
 Exponentially worsening problem is “DARK SILICON “ to be the primary
force that dictates the evolution in the processor.
 Dark Silicon Age kicked off with the transition to multi core. For every new
generation of process the percentage of the transistors that a chip can switch at
full frequency is dropping exponentially due to power constraints

5. UTILIZATION WALL
Utilization wall dictates that due to poor CMOS scaling,
improvements in processor performance are determined not by
improvements in transistor frequency or transistor count, but rather by the
degree to which each process shrink reduces the switching energy for
underlying transistors.

6. BASIC DEFINITIONS
 TRANSISTORS : A transistor is a semiconductor device used to
amplify and switch electronic power and signals.
 MICROPROCESSOR : The microprocessor is a programmable device
that accepts digital data as input, processes it ,stored in its memory, and
provides results as output .
 MULTICORE : A multi-core processor is a single computing
component with two or more independent actual processing units which are
the units that read and execute program instructions.
 SILICON : A small piece of semiconducting material on
which integrated circuit is embedded.

7. PROPOSED SCHEMES
 C-cores.
 Greendroid.

8. MOORE’S LAW
The observation that, over the
history of computing hardware,
the “number of transistors in a
dense integrated circuit doubles
approximately every two years”.

9. DESIGN GOALS
 Low complexity.
 Easy of integration .
 Capability.
 Utilization wall is a fundamental first order constraint for processor design.
to predict this CMOS scaling theory is used.
 The architectures needed to be created that can leverage many transistors
without actually actively switching them all.

10. GREENDROID ARCHITECTURE
 Greendroid processor combines
general purpose processor with
application specific processor that
are very efficient.
 Greendroid is a heterogeneous tiled
architecture. The tiles caches are
kept coherent through a simple
cache coherence schemes that
allows caches of inactive tiles to be
collectively used .
 Greendroid tiles however are not
uniform each of them contain
unique collection of 8 to 15 cores.

11. Android : Green droid's Target Workload.
 Android is an excellent target for
Greendroid-Style Architecture.
 Android comprises of three main
components Linux kernel, a
collection of native libraries and
Dalvik virtual machine.(DVM)
 Android’s usage model also
reduces the need for the patching
in architecture.
 This architecture also includes a
mesh-based on-chip network.

12. Conservation Cores
 It is known as C-Cores
specialized coprocessors.
 C-cores are a post –multicore
approach that constructively
reduces the energy consumption
of an application by 10x or more.
 These cores target specific
Android hotspots, including the
kernel.
 C-cores concept by applying the
technique to the Android mobile
software stack in order to build a
mobile application processor that
runs the applications with a
fraction of the energy
consumption..

13. LIFE CYCLE
 C-cores are paired with energy
efficient general purpose host
CPU and perform all their
memory operations through data
cache.
 Frequently executed hot code
regions are implemented using C-
cores while cold regions are
executed on the host CPU.
 C-cores generally have slight
improvements in performance
versus general purpose cores.
They can have up to 18x
improvement in energy efficiency.

14. GENERATION OF C-Core
 It is relatively a straight forward process .
 It is parallelism and regularity-agnostic and employs a function call.
Passes through compiler which code reconstitution.
 Supports CFG’s ,data structures and arbitrary memory access patterns etc.
 After code is been reshaped then respective control flow diagrams and data
flow diagrams are drawn for respective process.
 Each instruction in the basic block is directly converted into hardware
operator.
 The live-ins of the DFD’s are turned into register. The control logic is
created control logic that sequences the multiplexed operators and stalls the
sequencing logic appropriately on a cache miss. This logic represented by
using Verilog.

15. METHODOLGY
GREENDROID
 To reduce the energy consumption a
mobile application processor is introduced.
 It serves as an prototype for mobile
application processor.
 Greendroid is research prototype that
demonstrates the use of cores that saves
energy across the hotspots in the Android
mobile phone software stack.
 A single Greendroid processor will
contain tens or hundreds of different cores
that each implement a different key
function in Android.
 Greendroid attacks one of the most
important realities of Moore’s Law.

16. SYNTHESIZING C-CORES FOR GREEENDROID
 C-core tool chain converts arbitrary c functions into C-core hardware.
 This tool chain targets a much wider range of C constructs and build
energy saving C-cores for functions that are poor targets for acceleration.
 The tool chain’s profiling pass identifies “hot” functions and loops in the
target workload and isolates them by in lining functions and outlining
loops.
 The data path mirrors the single static assignment program representation
the compiler uses internally and groups instruction together by basic block.
 The control path tracks the execution through function with a state machine
that closely matches the function’s control flow graph .

17. Ctnd..
 The compiler also generates function stubs to replace the original
functions by invoking the hardware.
 C-cores support this by providing targeted reconfigurability that lets them
to maintain perfect fidelity to changing source code.
 C-cores provide built-in support for changes to compile-time constants as
well as general mechanism for transferring the control back to core to
execute the individual basic block.

18. RESULT
GreenDroid leverage "dark silicon" to dramatically reduce energy
consumption by integrating conservation cores in smartphone .C-cores
also incorporate focused reconfigurability that allows them to adapt to
small changes in the target application while still realizing efficiency gains.

19. Future Scope
“Turbo mode “that runs some cores faster if others are switched off. We
can expect similar trends for future of mobile processors as well.

20. CONCLUSION
The severity of the problem is to develop new architectural
tradeoffs that trade Dark Silicon , an exponentially cheapening resource
,for energy which is the true limiter of performance today. Conversation
cores and Greendroid offers potential way to attack the Dark silicon
problem.