Reconfigurable ProcessorsReconfigurable Processors

By : Kulbhushan Kashyap

Contents

• Introduction• History• How the reconfigurable processors built?• Introduction to FPGAs• Classification• Examples• Trade-off bet’n flexibility and performance• Advantage and disadvantage

Reconfigurable ProcessorsReconfigurable Processors

• A microprocessor with erasable hardware that can rewire itself dynamically.

• Ideally, the reconfigurable processors can transform itself from one form to another form. Like same chip use as a video chip to a central processing unit ( CPU ) to a graphics chip.

History:• In 1960 Gerald Estrin, a computer scientist at the university of california, proposed the idea of fixed plus variable structure computer.• It would consist of a standard processor, augmented by the array of

reconfigurable hardware, the behavior of which could be controlled by the main processor.

• Reconfigurable hardware could be setup to performance a specific task, such as image processing or pattern matching.

• Once task has done the hardware could be required for something else.• Result of this is hybrid computer, combining the flexibility of software

with the speed of hardware.• He try to made it at that time but failed to catch it on.

How the reconfigurable processors built?

Recipe 1:

• Take one ,two ….Field Programmable Gate Arrays(FPGAs)• Take conventional processor• Combine both • Either tight on the same die • or through PCI-X, Memory, coprocessor interface

Recipe 2:

• This is simple one • Use a softcore processor on FPGAs

Introduction :What is FPGAs?

• Hardware to implement one or many logic functions• logic of function can be change after production• consist of configurable logic block• configuration is loaded with bit file

Configurable logic block:

• 1 CLB = 4 slices• 1 slice = 2 LUTs• Flipflops• form shift register• sometimes adder and multiplier

Reconfiguration :

• special feature of FPGAs• parts of FPGAs can be change while other parts are computing

A Very Simple Processor:

Classification:

What kind of architecture is present?

• Functional unit based• Co-processor based • Soft-/hardcore based• Single and multicore based

• different kind of FUs• ALU, Multiplier,…..• no direct memory access is available• mostly no internal state

Functional unit based:

Coprocessor based:

• coprocessor interface used (ARM based)• RAM interface(x86 based)• often internal state available• version 2: direct memory access so file transfer rate increase

Soft-/hardcore based:

• Hardcore based : everything till now• Soft core based : processor configured onto FPGAs

• simple adaption of core • flexible configuration

Multicore based:

• many heterogeneous cores possible• different processor types (ARM,x86,mips…..)

• Processor cores built out of a repertory of components

Real world examples :Intel Atom + Altera FPGA

Examples :Multicore Reconfiguration Platform

• Shows three abstraction layer

Trade-off between flexibility and performance

• General purpose processors gives more flexibility and less performance• ASICs gives less flexibility and more performance• Reconfigurable processors gives both flexibility and performance

Advantage :

• It is easier to design and implement compare to ASICs.• They are highly optimized and very complex designs, very

general purpose, in that it gives very huge rang of application.

• Microprocessor or software programmable architectures in general, the perfect case of IP reuse.

• SoC concept is almost 10 year old, which is claimed that microprocessor are the only kind of hardware IP that

effectively allows reuse.

Disadvantage :

• It is slower and more expensive. Hard-wired chips are the oldest, cheapest, and fastest - but also the least flexible of all the options.

Bibliography

• www.google.com• www.xilinx.com• www.altera.com

THANK YOU