The shared control parallel architecture model

SIMD machines are considered special purpose architectures chiefly because of their inability to support control parallelism. This restriction exists because there is a single control unit that is shared at the thread level; concurrent control threads must time-share the control unit (they are seque ntially executed). We present an alternative model for building centralized control architectures that allows better support for control parallelism. This model, called shared control, shares the control unit(s) at the instru ction level. More precisely, in each cycle the control signals for all the supported instructions are broadcast to the PEs. In turn, each PE receives its control by synchronizing with the control unit responsible for its loca l instruction. The shared control model is Fundamentally different from the SIMD model. There are a number of architectural issues that must be resolv ed in order For this model to be useful. This paper identifies some of thes e issues and discusses their respective trade-off spaces. An integrated sha red-control SIMD architecture design (SharC) is presented and used to demon strate the relative performance relative to a SIMD architecture. (C) 2001 A cademic Press.