HADES-an asynchronous superscalar processor

Hades is a generic processor architecture suitable for both single and multiple-instruction-issue asynchronous implementation. This paper discusses Hades, emphasising performance in the presence of instruction sequences exhibiting Read-After-Write (RAW) dependencies. Two schemes are considered. Firstly, a register file optimisation that allows easier read access to data in the case of RAW dependencies. Secondly, an operand forwarding mechanism, Decoupled Operand Forwarding, that forwards data between instructions yet separates forwarding from other pipeline operations. Hardware simulations of Hades indicate that register file optimisation improves performance by 6% and Decoupled Operand Forwarding increases performance by 15%; in combination performance is bettered by 16%. A further result suggests that optimising asynchronous communication in Hades improves performance by 30%