Directional and SingleDriver Wires in FPGA Interconnect Guy
- Slides: 41
Directional and Single-Driver Wires in FPGA Interconnect Guy Lemieux Edmund Lee Marvin Tom Anthony Yu Dept. of ECE, University of British Columbia Vancouver, BC, Canada
Outline • Motivation • Bidirection vs. Directional – New detailed routing architecture – Which is better? • Tristate vs. Single-Driver – HSPICE results – Which is better? • Place & Route Results • Conclusions
Motivation: Bidirectional Wires Interconnect Logic
Motivation: Bidirectional Wires Problem Half of Tristate Buffers Left Unused Buffers Dominate Size of Device
Bidirectional vs. Directional Wiring
Bidirectional vs Directional
Bidirectional vs Directional
Bidirectional vs Directional
Bidirectional vs Directional
2 -Dimensional FPGA aka Island-Style or Mesh
Bidirectional Switch Block
Directional Switch Block
Bidirectional vs Directional Switch Block: Directional has Half as Many Switch Elements Switch Element: Same Quantity and Type of Circuit Elements (twice the wiring)
Building up Long Wires Start with One Switch Element Wire ends for straight connections.
Building up Long Wires Connect MUX Inputs Extend MUX inputs
Building up Long Wires Connect MUX Inputs TURN UP from wire-ends to mux
Building up Long Wires Connect MUX Inputs TURN DOWN from wire-ends to mux
Building up Long Wires Add +2 More Wires (4 total) Add LONG WIRES, turning UP and DOWN.
Building up Long Wires Add +2 More Wires (6 total) Add LONG WIRES, turning UP and DOWN
Building up Long Wires Single Layout Tile !!! Add wire twisting
Long Wires! 1 2 3 NOTICE: One switch element holds 6 wires #Wires : = Wire. Length x Num. Directions = 3 x 2 = 6 No “partial” switch elements with fewer wires
Small Switch Block One L 3 Switch Element
Bigger Switch Block Two L 3 Switch Elements NOTICE Switch element design forces quantization of channel width Bidirectional One quantum = 1*L Directional One quantum = 2*L
Summary • Directional wiring – Good • Potential area savings – Bad • Big input muxes, slower • Bigger quantum size (2*L) • Detailed-routing architecture is different (need new switch block) – Need to evaluate!
Tristate vs. Single-driver Wiring
Bidirectional Wiring Outputs are Tristates Fanout increases delay Multi-driver Wiring!!! Bidir Architecture
Directional Wiring Outputs can be Tristates Fanout increases delay Multi-driver Wiring!!! Dir-Tri Architecture
Directional Wiring Outputs can use switch block muxes New connectivity constraint Single-driver Wiring!!! Dir Architecture
Tristate HSPICE Model
Tristate HSPICE Model
Single-driver HSPICE Model
HSPICE Delays Includes Switch + Wire TSMC 0. 18 um
AREA * HSPICE Delay TSMC 0. 18 um
Summary • Single-driver wiring – Good • Same delay as tristate • No delay increases caused by fanout • Fewer wire loads: 27% lower capacitance – Bad • Directional only (by necessity) • Area-delay product “seems” worse, but isn’t
Place and Route Results
Channel Width
Area (Transistor Count)
Delay
Area-Delay Product
Results Summary • Average improvements usingle-driver wiring 0% channel width 9% delay 14% tile length of physical layout 25% transistor count 32% area-delay product 37% wiring capacitance
Conclusions • No more tristates! – Eliminates need for pass transistors – No “Vt” loss signal degradation – Better signal reliability, better drive strength • Significant savings in all metrics – Any reasons left to use bidirectional wiring ? ? ? • Savings INCREASES with circuit size – Because interconnect dominates big circuits
- Operationalised directional hypothesis
- What is directional and non directional hypothesis
- Directional and non directional hypothesis
- Directional and non directional hypothesis
- 2.58 z score
- Directional and non directional hypothesis
- Directional vs non directional hypothesis
- Taktik good guy bad guy
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- Virtual protocol interconnect
- Optical interconnect
- Optical interconnect solution
- What is topology
- Programmable interconnect
- Rating billing
- Cross building interconnect
- Hyper transport
- Wishbone interconnect
- Chet mehta
- Dolphin interconnect
- Open systems interconnect
- High frequency interconnect
- Interconnect scaling
- Interconnect
- Dspx simulation suite
- Flexible interconnect
- Interconnect
- Ring interconnect
- Lumerical interconnect
- Ground live neutral
- Ground neutral live
- Cpld fpga
- Prom circuit diagram
- Tripping over wires
- How do the wires keep the spotlight centered
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- 2-wires door entry system design
- How to measure 45 minutes using two identical wires
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- Principles of wires