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Early Output Logic with Anti-Tokens

Early Output Logic with Anti-Tokens. Charlie Brej, Jim Garside APT Group Manchester University. Outline. Asynchronous Logic DIMS (Delay Insensitive Minterm Synthesis) Early Output Logic Guarding Anti-Tokens Collisions Conclusions. Asynchronous Latch. Ri. Ro. Latch. Ai. Ao. Req.

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Early Output Logic with Anti-Tokens

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  1. Early Output Logic with Anti-Tokens Charlie Brej, Jim Garside APT Group Manchester University Early Output Logic with Anti-Tokens

  2. Outline • Asynchronous Logic • DIMS (Delay Insensitive Minterm Synthesis) • Early Output Logic • Guarding • Anti-Tokens • Collisions • Conclusions Early Output Logic with Anti-Tokens

  3. Asynchronous Latch Ri Ro Latch Ai Ao Req Ack Early Output Logic with Anti-Tokens

  4. Asynchronous Pipeline Early Output Logic with Anti-Tokens

  5. Asynchronous Pipeline Stall Wait! Early Output Logic with Anti-Tokens

  6. Dual-Rail Latch • Dual-Rail • 00 = ‘NULL’ • 01 = 0 • 10 = 1 • 11 = Illegal • Return to ‘NULL’ Ri_0 Ro_0 Ri_1 Ro_1 Latch Ao Ai Early Output Logic with Anti-Tokens

  7. DIMS Logic C 0 C 0 C 1 C Early Output Logic with Anti-Tokens

  8. C C C C DIMS vs Early Output Logic Size:48 transistors Delay:4 inversions Size:12 transistors Delay:2 inversions Early Output Logic with Anti-Tokens

  9. Early Output Logic 0 0 1 Early Output Logic with Anti-Tokens

  10. Guarding Problem: • Inputs • Late • Unnecessary • Acknowledge before ready Solution: • Validity signal (Vo) Ri Ro Vo Latch Ao Ai Early Output Logic with Anti-Tokens

  11. Early Output Guarding 0 0 C 1 Early Output Logic with Anti-Tokens

  12. Anti-Tokens Don’t: • Stall entire stage until late input arrives Do: • Stall the latch instead • Early ‘Validity’ • Acknowledge before Data Early Output Logic with Anti-Tokens

  13. Anti-Token Generation 0 0 C A Early Output Logic with Anti-Tokens

  14. Anti-Token Propagation A A C A Early Output Logic with Anti-Tokens

  15. Token Pass T T T Early Output Logic with Anti-Tokens

  16. Anti-Token Pass A A A Early Output Logic with Anti-Tokens

  17. Token Anti-Token collision T T A Early Output Logic with Anti-Tokens

  18. Token Anti-Token collision 2 T ? A Early Output Logic with Anti-Tokens

  19. Dual-Purpose Signals • Arbiter free • Req: • Token Request • Anti-Token Acknowledge • Ack: • Anti-Token Request • Token Acknowledge Req Ack Early Output Logic with Anti-Tokens

  20. Conclusions • New, fine-grain, asynchronous pipeline • Faster than DIMS (2x) • Smaller than DIMS (4x) • Lower power than DIMS • Some speed advantages over synchronous designs • Counterflow - no arbitration • Requires some timing assumptions Early Output Logic with Anti-Tokens

  21. Timing Hazard example 0 A 0 C A Early Output Logic with Anti-Tokens

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