Transcript Topic Review: FPGA vs. ASIC

Steve Poret
RCS – ENG 6530
June 10, 2008
[1] Measuring the Gap between FPGAs and ASICs

Ian Kuon and Jonathan Rose

The Edward S. Rogers Sr. Department of Electrical and Computer Engineering

University of Toronto, 2006
[2] (When) Will FPGAs Kill ASICs?
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Rajeev, Jayaraman
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Xilinx Inc.
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DAC-2001
[3] ASICs Verses FPGAs

Frank J. Bartos
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Control Engineering

6/1/2005
[4] Structured ASICs

Dan Lander, Haru Yamamoto, Shane Erickson
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UCLA - EE 201A

Spring 2004
[5] Signal, Timing Integrity Assured with FPGAs - Technology Information

Rich Sevcik

Electronic News

July 24, 2000
[6] Navigating the Silicon Jungle: FPGA or ASIC?

Blyler, John

Chip Design Magazine

June/July 2005
[7] FPGA vs. ASIC
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Xilinx Inc.
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Getting Started with Xilinx

2006
[8] Xilinx: Virtex-5 Family Overview
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Xilinx Inc. datasheet
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DS100(v4.2) May 7, 2008
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Introduction
Performance Perspective
◦ Measuring the Gap between FPGAs and ASICs, [1]
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Cost/Risk/Lifecycle Perspective
◦ (When) Will FPGAs Kill ASICs?, [2]
◦ ASICs verses FPGAs, [3]
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
Summary
Future Technology
◦ Structured/Platform ASICs, [4]
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Conclusion
ASIC (Application Specific Integrated Circuit)
◦ An IC designed for a particular use
◦ Standard cell, full-custom ASIC
Applications
◦ Processors
◦ RAM
◦ ROM
Why are we interested?
◦ The size of transistors are shrinking to sub-micron
levels
Deep Sub-Micron (DSM) designs have problems
 Two main fundamental issues:
◦ Signal Integrity
◦ Timing Closure
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Is an ASIC still the best architecture?
FPGA (Field Programmable Gate Array)
◦ Logic blocks and programmable interconnects
◦ Synthesis tools are designed to counter DSM issues
Applications
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ASIC Prototyping
Massive parallelism (code breaking, cryptography)
DSP, SDR, medical imaging
FFT

Implementation medium: FPGA or ASIC?
◦ Based on:
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Area
Performance
Power consumption
Cost
Time-to-market
Design Cycle
Complexity of design
How do we measure the gap between FPGAs
and ASICs?
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New FPGA vs. ASIC comparison, (Kuon, Rose)
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System Architecture:
◦ Altera Stratix II (FPGA)
◦ STM CMOS090 Design Platform standard cell (ASIC)
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Look at previous comparisons: inadequate
Authors took many considerations to ensure
most accurate possible comparison
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Chose 23 benchmark designs
Implement all benchmarks in
both FPGA and ASIC
Compare:
◦ Silicon Area
◦ Maximum Operating Frequency
◦ Power Consumption
Silicon Area
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Hard DSP blocks significantly reduce
the area gap (40 -> 28)
Memories slightly reduced
(40 -> 37)
All components utilized (40 -> 21)
Introduction of heterogeneous
blocks are very important in
decreasing FPGA area
Speed
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Hard DSP blocks increase delay?
◦ The multipliers are fixed size, thus will
slightly decrease performance, but the
additional time comes with extra routing to
accommodate for fixed positions of DSPs.
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Memories
◦ 3.2 -> 2.3, offer speed-up vs. ASIC design,
but slow low power memory is used in the
ASIC, and is no real advantage vs. newer
memory
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Overall, the memory blocks offer the
same advantage as the DSP blocks:
primary benefit is improved area
efficiency
Speed
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Fastest speed is useful for
understanding the best case
solution, but not fair to ASIC.
ASICs are generally designed for
worst-case process
As seen the performance gaps are
respectively larger, confirming that
ASICs perform faster then FPGAs.
2.8 times faster
Power Consumption
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FPGAs consume 9-to-12 times the
amount of power as an ASIC
Area savings suggest a slight
power reduction as less wires &
components are used
Introducing DSP and/or memory
blocks to the FPGA reduce power
consumption
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Presented empirical measurements
quantifying the gap between FPGAs and ASICs
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FPGA design is 21-40 times larger than an
standard-cell ASIC design
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FPGA is 2.1-4.5 times slower than a
standard-cell ASIC design
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FPGA consumes 9-12 times more power than
ASIC
Clearly ASICs have better performance than
FPGAs, though they lack the flexibility
So why are FPGAs even used?
Non-performance factors:
 Unit costs
 Non Recurring Engineering (NRE) costs
 Time to market
 System reconfigurability
 Design cycle
 Volume/Gate Count/Freq/IP requirements
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Unit cost analysis
◦ ASIC: lower unit costs for high volumes
◦ ASIC: design tools tend to cost more
◦ FPGA: No upfront NRE - costs typically associated
with an ASIC design
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Exploding (NRE) ASIC Cost
High mask costs as process
geometry decreases
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Time to market
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System reconfigurability
Lack of reconfigurability is a large opportunity cost of
ASICs as FPGAs offer flexible design cycle management
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Design Cycle
ASIC: very unforgiving (no late changes)
FPGA: flexible to allow late design changes
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Volume Requirements (Unit cost)
ASICs are cost effective for large volumes
(> 250,000)
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Gate Count Requirements
FPGAs have limited gate count: 3 million
(2000)
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Performance Requirements (Speed)
FPGAs can operate up to 200Mhz (2000)
Note: 550Mhz Xilinx Virtex-5 (2008)
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IP in FPGAs
◦ 1995 – Only gates and routing
◦ 2000 – Multiple I/O standards, clock management,
RAM, multipliers, processors
◦ 2008 – Ethernet, GTP/GTX transceivers,
microprocessors, 65-nm technology, DCM,
PLLs, 12 routing layers, triple-oxide for
reduced power consumption
◦ 20xx – Power down individual sections of FPGAs?
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Traditionally, ASICs are used for large
projects and FPGAs for smaller projects that
need to get to market faster, or can benefit
from remote upgrades
Improved FPGA performance, density, and
fabrication cost are pushing the ASICs out of
the market; as the key remains FPGAs quick
time-to-market value
 2 years for ASIC, verses 9 months for FPGA
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Earlier FPGAs were only viable for prototyping or
low-density applications; now they see very highvolume usage in consumer products and other
moderate volume high-density applications
Highest-density FPGAs (90 nm) still have a
definitive higher unit price than ASICs
However, cost trade-offs often favour FPGAs even
with these highest density applications, when
development and NRE charges are factored in
David Greenfield, senior director of high-density FPGAs at Altera Corp
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Upfront development investment is higher with a
cell-based ASIC approach
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At high volumes, ROI is significantly better due to
smaller die size and lower per unit costs.
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FPGAs tend to be a better choice where unit price is
less important, or time-to-market, or low initial
development cost drives the solution
FPGAs and structured ASICs are suitable for low
volume, short lifetime applications where customers
can compromise on functionality and performance
while still achieving their system objectives
John DiFilippo, silicon architect for TI's ASIC Communications
Infrastructure Business Unit
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FPGAs are closing in on ASICs for
performance values, even though ASICs are
smaller, faster and more efficient at the
moment
FPGAs provide cost, time, reconfigurability
and flexibility over ASIC designs which make
them attractive
Gap is narrowing between the technologies
Structured ASICs
 Newer term in the industry
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The logic mask layers of a device are predefined
by the ASIC vendor
Design differentiation and customization is
achieved by creating custom metal layers that
create custom connections between predefined
lower layer logic elements
Because only a small number of chip layers must
be custom-produced, structured ASIC designs
have much smaller NRE costs than other ASIC
chips, which require that a full mask set be
produced for every design
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Both manufacturing cycle time and design
cycle time are reduced compared to standard
cell-based ASIC by:
 Pre-defined metal layers
 Pre-characterization of what is on the silicon
 Pre-defined power, clock, test structures
Routing Layer
Routing Layer
Pre-Routed Layer
Pre-Routed Layer
Pre-Routed Layer
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FPGA vendors have also designed their own
version of the structured ASICs:
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Altera (HardCopy)
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Xilinx (EasyPath)
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Both designs have the programming capabilities
removed
◦ Same design cells as FPGA, but programmable routing
replaced with fixed wire interconnects
◦ “customer specific FPGA”; 30-70% cheaper than standard
FPGA, same standard FPGA cells
Advantages
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Mainly used for mid-density designs
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High performance (close to standard-cell)
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Low power consumption
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Less complex (fewer layers to fabricate)
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Small time-to-market (pre-defined cell blocks)
Disadvantages
 Design tools
 Expensive
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Immature architecture
◦ Therefore have not been formally evaluated and
compared;
 Tradeoffs within the architecture (LUTs, RAM size)
Parameter
FPGA*
Structured ASIC
Standard-cell ASIC
Area
40
10
1
Speed
4.5
1.5
1
Power consumed
12
2
1
Unit costs
High
Medium
Low (high V)
NRE cost
Low
Medium
High
Time-to-market
Low
Low-Medium
High
Reconfigurability
Full
No
No
Market Volume
Low-medium
Medium
High
*used worst-case values
(from Kuon, Rose)
Structured ASICs have many of the advantages
of both FPGAs and standard ASICs
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FPGAs, Structured ASICs and ASICs each have
their own advantages and disadvantages
◦ ASICs
 High costs, high performance
 Low flexibility
 Difficult and long design cycle
◦ FPGAs
 Low cost, low performance
 Reconfigurable
 Quick and easy for designers
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Do you have any questions?

Project …..
Project Outline:
 Start with 1-bit ALU design using VHDL (Xilinx)
 Modify an ALU from a 4-bit to 16-bits
 Add other capabilities to the ALU (Multiplication, Division)
 Duplicate the ALU to max capacity of the FPGA
 The ALUs are connected using different connections:
◦ Bus
◦ Point-to-point matrix connection


Comparisons between the two implementations
Solve Benchmarks
TERM PROJECT
Project Outline:
 Start with 1-bit ALU design





Re-learn VHDL code
Modify an ALU from a 4-bit to 16-bits
Add other capabilities to the ALU (Multiplication, Division)
Duplicate the ALU to max capacity of the FPGA
The ALUs are connected using different connections:
◦ Bus
◦ Point-to-point matrix connection


Comparisons between the two implementations
Solve Benchmarks
TERM PROJECT