1 / 14

Bundled-Data Datapaths

Bundled-Data Datapaths. Problems random standard cell layout mixed control + datapath timing analysis required robustness of design reduced Possible Solutions DI codes hybrid bundled + DI simpler timing analysis. DI Codes. Dual Rail (used in 1st Tangram system)

carlyt
Télécharger la présentation

Bundled-Data Datapaths

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bundled-Data Datapaths • Problems • random standard cell layout • mixed control + datapath • timing analysis required • robustness of design reduced • Possible Solutions • DI codes • hybrid bundled + DI • simpler timing analysis

  2. DI Codes • Dual Rail (used in 1st Tangram system) • Can use standard cell approach without timing analysis • no need to distinguish between control & data • abandoned in favour of bundled-data • area cost in extra wires • area & time cost in completion detection • Tangram/Balsa generates push-pull pipelines with expensive synchronization

  3.  • c c o i B B Generic Pipeline • Passivators join compiled procedure passivator

  4. C C Passivator Implementation • Bundled Data ar br C aa ba n-wide C-gate data[n] • Dual Rail d0 br d1 n-bits wide dn-1 aa ba

  5. DI Code Synchronizations • Expensive • need C-element synchronisation tree • A partial solution (not always possible/desirable) is: • transform to push-style datapath • (not possible in Tangram only Balsa)

  6.  c c o i • B B Push Pipeline Passive input port connector (wires-only)

  7. Hybrid Solutions • Use DI coding within bundled datapath framework • e.g. use dual-rail carry signals within a conventional adder • early completion easily detected • Average-case performance • Only applicable to a few datapath operations

  8. Simpler Timing Analysis • Separate control and datapath • generate regular, compiled, datapath • area improvement over standard cell (because of regular layout) • generate matched delay paths (c.f. self-timed PLAs) • must be able to recognize datapath • difficult: control often contains datapath-like elements. • e.g. start at variables and work backwards ...

  9. Datapath meets Control • Example: Balsa case statement 1 hot encoding data “n” bits wide true/complement lines: dual-rail expansion

  10. Case Component • input from datapath • dual-rail simplifies internal logic • expansions parameterisable • “encode” component is similar • opposite of case with true/false expansion

  11. Simpler Timing Analysis • Tool support required • use existing (non-Balsa) tools if possible • automatically add matched paths/delays to synthesised datapaths • Design own cells where appropriate • e.g. hybrid stages

  12. Future Work • Provide support for DI, hybrid and datapath-compiled datapaths • even with datapath compilation, some datapath would still be standard cell • e.g. instruction decoder (control heavy) • datapath in control • cost of connecting separate blocks in layout • Test Design required (datapath heavy)

  13. Tool Enhancement • balsa-c • support for attribution to select compilation mechanisms/ optimisation schemes • breeze2lard • new models • balsa-netlist: • new tech-mapping descriptions • interface to datapath compilers

  14. DMA Controller Floor-Plan

More Related