In this paper we develop a general approach to global reactive congestion control in multicomputer networks. The approach uses a timeout mechanism to detect congestion, and exploits control lines such as those used for handshaking in the flit-level flow control of wormhole routers to distribute information about congestion. It is also based on a mechanism that limits the demands placed by the network interface and the processing element. The approach is described in detail and evaluated through simulation experiments. We show that the proposed congestion control can provide network stability and predictable network performance. By choosing the right timeout, we can provide bounds on average delay and worst-case delay. Furthermore, with appropriate timeouts the network can be kept out of saturation. Other attributes of the approach include fairness and applicability to a wide range of network architectures.

We propose a new prioritized demand multiplexing (PDM) scheme for wormhole networks. Conventional demand multiplexing allows a set of ready flits to share a physical link in a strict round robin manner Thus, it does not allow flexibility for fast movement of high priority messages. The proposed PDM scheme allows a virtual channel, containing flits of a high priority message, to use its associated physical channel for multiple number of successive clock cycles. We present motivation behind the proposed PDM scheme, description of the scheme, and implementation issues. The study suggests that allowing a virtual channel with a high priority message to use 2 successive clock cycles is sufficient to provide up to 35% reduction in latency for high priority messages. The results demonstrate significant potential for designing high performance wormhole systems to support efficient implementation of applications with hybrid traffic characteristics.

The type system of a programming language system PL/LL is described. PL is a simple object oriented programming language and LL is a language for composing PL modules into programs. The goals of the PL/LL system are to enable the programming of efficient object-oriented computations and to provide the powerful linking language LL for facilitating the construction of large programs. The goal of the type system is to ensure efficient and secure object handling through a combination of static and dynamic type checking, and to preserve this property across module boundaries. The solution is based on (i) the module and linking concepts of LL, (ii) a language construct in PL for the safe creation of linked data structures, and (iii) a limited form of type polymorphism and type unification.

Abstract A monitor suitable for small computers is described. It implements processes and synchronization primitives. A time queue mechanism with the possibility of time‐limited waiting for signals is also provided. Processes have fixed priorities determining allocation of processor time. The monitor allows dynamic creation and deletion of processes. Each process has a local data area and access to the registers of the processor and a global stack on a temporary basis.