MASCOT: Microarchitecture synthesis of control paths

Abstract

This paper presents MASCOT (MicroArchitecture Synthesis of ConTrol paths). This synthesis system constructs the optimal microarchitecture for a control path of an instruction set processor. Input to the system is the behavioural specification of a control path. This specification is in finite state machine form which is mapped initially onto a single programmed logic array (PLA) microarchitecture. The synthesis strategy then applies a sequence of decompositions on this initial microarchitecture. This strategy follows a decision scheme until all design objectives are met. It transforms the initial microarchitecture into a complex microarchitecture of several PLAs and ROMs. Where it is impossible to meet the design objectives, the system constructs a microarchitecture which comes as close as possible to given design objectives. Design objectives are allowed on floorplan dimensions and delay. Our strategy integrates a number of known optimization methods for specific microarchitectures. Therefore this synthesis method explores a larger part of the design space than do other control path synthesis methods. Other methods are mostly bound to one microarchitecture which they optimize. Our system is not only very flexible in microarchitecture construction but also open for extension by other optimizations.