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System-on-a-chip. Design methods to facilitate rapid growth of SoCs Arvind Computer Science & Artificial Intelligence Lab Massachusetts Institute of Technology. The biggest SoC drivers. Explosive growth in markets for cell phones game boxes sensors and actuators.

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System-on-a-chip

Design methods to facilitate rapid growth of SoCs

Arvind

Computer Science & Artificial Intelligence Lab

Massachusetts Institute of Technology

http://csg.csail.mit.edu/arvind


The biggest soc drivers
The biggest SoC drivers

  • Explosive growth in markets for

    • cell phones

    • game boxes

    • sensors and actuators

Functionality and applications are constrained primarily by:

- cost

- power/energy constrains

http://csg.csail.mit.edu/arvind/


Current cellphone architecture

WLAN RF

WCDMA/GSM RF

WLAN RF

WLAN RF

Comms. Processing

Application Processing

Current Cellphone Architecture

Today’s chip becomes a block in tomorrow’s chip

IP reuse is essential

Hardware/software migration

IP = Intellectual Property

Complex, High Performance

but must not dissipate more than 3 watts

http://csg.csail.mit.edu/arvind/


An under appreciated fact
An under appreciated fact

  • If a functionality (e.g. H.264) is moved from a programmable device to a specialized hardware block, the power/energy savings are 100 to 1000 fold

Power savings  more specialized hardware

but our mind set

  • Software is forgiving

  • Hardware design is difficult, inflexible, brittle, error prone, ...

http://csg.csail.mit.edu/arvind/


Soc trajectory multicores heterogeneous regular

IBM Cell Processor

On-chip memory banks

Application-specific processing units

General-purpose processors

Structured on-chip networks

SoC Trajectory:multicores, heterogeneous, regular, ...

Can we rapidly produce high-quality chips and surrounding systems and software?

http://csg.csail.mit.edu/arvind/


Things to remember
Things to remember

  • Design costs (hardware & software) dominate

  • Within these costs verification and validation costs dominate

  • IP reuse is essential to prevent design-team sizes from exploding

design cost = number of engineers x time to design

http://csg.csail.mit.edu/arvind/


Common quotes

Almost complete reliance on post-design verification for quality

Mind set

Common quotes

  • “Design is not a problem; design is easy”

  • “Verification is a problem”

  • “Timing closure is a problem”

  • “Physical design is a problem”

http://csg.csail.mit.edu/arvind/


Through the early 1980s

Make quality

Inspect

Rework

Defect

Defect

Defect

Through the early 1980s:

The U.S. auto industry

  • Sought quality solely through post-build inspection

  • Planned for defects and rework

    and U.S. quality was…

http://csg.csail.mit.edu/arvind/


Less than world class
… less than world class quality

  • Adding quality inspectors (“verification engineers”) and giving them better tools, was not the solution

  • The Japanese auto industry showed the way

    • “Zero defect” manufacturing

http://csg.csail.mit.edu/arvind/


New mind set design affects everything
New mind set: qualityDesign affects everything!

  • A good design methodology

    • Can keep up with changing specs

    • Permits architectural exploration

    • Facilitates verification and debugging

    • Eases changes for timing closure

    • Eases changes for physical design

    • Promotes reuse

 It is essential to

Design for Correctness

http://csg.csail.mit.edu/arvind/


New ways of expressing behavior to reduce design complexity
New ways of expressing behavior to reduce design complexity quality

  • Decentralize complexity:Rule-based specifications (Guarded Atomic Actions)

    • Lets you think one rule at a time

  • Formalize composition: Modules with guarded interfaces

    • Automatically manage and ensure the correctness of connectivity, i.e., correct-by-construction methodology

Strong flavor of Unity

Bluespec

  • Smaller, simpler, clearer, more correct code for both simulation AND synthesis

http://csg.csail.mit.edu/arvind/


Reusing ip blocks

data_in qualitypush_req_npop_req_nclkrstn

data_outfullempty

Reusing IP Blocks

Example: Commercially available FIFO IP block

No machine verification of such informal constraints is feasible

These constraints are spread over many pages of the documentation...

http://csg.csail.mit.edu/arvind/


Bluespec promotes composition through guarded interfaces

theFifo.enq(value1); quality

Enqueue arbitration control

theFifo.deq();

value2 = theFifo.first();

enab

not full

rdy

enab

not empty

rdy

not empty

theFifo.enq(value3);

rdy

Dequeue arbitration control

theFifo.deq();

value4 = theFifo.first();

Bluespec promotes compositionthrough guarded interfaces

Self-documenting interfaces;

Automatic generation of logic to eliminate conflicts in use.

theModuleA

theFifo

n

enq

theModuleB

deq

FIFO

n

first

http://csg.csail.mit.edu/arvind/


Bluespec state and rules organized into modules

module quality

interface

Bluespec: State and Rules organized into modules

All state (e.g., Registers, FIFOs, RAMs, ...) is explicit.

Behavior is expressed in terms of atomic actions on the state:

Rule: guard  action

Rules can manipulate state in other modules only via their interfaces.

http://csg.csail.mit.edu/arvind/


The plan
The Plan quality

  • BS2- Simple Example: GCD

  • BS3- Combinational Circuits: IFFT

  • BS4- Architectural Exploration: 802.11a

  • BS5- The IP Lookup problem; subtle concurrency issues

  • BS6- Bluespec Semantics and Scheduling Primitives

Bluespec is available in two versions:

BSV – Bluespec in System Verilog

ESEPro – Bluespec in SystemC

These lectures will use BSV syntax

http://csg.csail.mit.edu/arvind/


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