Standard micropipelines use simple two-phase control circuits. The latches employed on AMULET1 are levelsensitive, so two-to four-phase converters are required in each latch controller. To avoid this overhead an investigation has been carried out into four-phase micropipeline control circuits; this has thrown up several design issues relating to cost, performance and safety, and forms a useful illustration of asynchronous design techniques.
An asynchronous implementation of the ARM microprocessor has been designed and fabricated based on Sutherland's Micropipeline approach. Reviews of this work have shown that considerable performance improvement may be possible in a number of key design areas. This paper assesses the effects of different design styles on the micropipeline latch structures used. The original design has latch structures based on passtransistor transparent latches. An evaluation of the use of single-phase transparent latch structures is given plus the application of 2-phase and 4-phase control techniques.
Abstract-An asynchronous implementation of the ARM microprocessor has been developed using an approach based on Sutherland's Micropipelines [1]. The design allows considerable internal asynchronous concurrency. This paper presents the rationale for the work, the organization of the chip, and the characteristics of the prototype silicon. The design displays unusual properties such as nondeterministic (but bounded) prefetch depth beyond a branch instruction, a data dependent throughput, and employs a novel register locking mechanism. This work demonstrates the feasibility of building complex asynchronous systems and gives an indication of the costs and benefits of the Micropipeline approach.
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