The Case for the Precision Timed (PRET) Machine

It is time for a new era of processors whose temporal behavior is as easily controlled as their logical function. We call them precision timed (PRET) machines. Our basic argument is that real-time systems, in which temporal behavior is as important as logical function, are an important and growing application; processor architecture needs to follow suit

uRT51: An Embedded Real-Time processor implemented on FPGA devices

In this paper we describe and evaluate the main features of the uRT51 processor. The uRT51 processor was designed for embedded realtime control applications. It is a processor architecture that incorporates the specific functions of a real-time system in hardware. It was described using synthesizable VHDL and it was implemented on FPGA devices. We describe how the uRT51 processor supports time, events, task and priorities. The performance of the uRT51 processor is evaluated using a control application as a case study. The experiments show that the uRT51 processor scheduling features outperform the ones obtained using a traditional RTOS-based real-time system.Fil: Cayssials, Ricardo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Duval, M,. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Ferro, Edgardo Carlos. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; ArgentinaFil: Alimenti, O.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentin

Reconciling Repeatable Timing with Pipelining and Memory Hierarchy

This paper argues that repeatable timing is more important and more achievable than predictable timing. It describes microarchitecture approaches to pipelining and memory hierarchy that deliver repeatable timing and promise comparable or better performance compared to established techniques. Specifically, threads are interleaved in a pipeline to eliminate pipeline hazards, and a hierarchical memory architecture is outlined that hides memory latencies

Tight WCRT Analysis for Synchronous C Programs

Accurate estimation of the tick length of a synchronous program is essential for efficient and predictable implementations that are devoid of timing faults. The techniques to determine the tick length statically are classified as worst case reaction time (WCRT) analysis. While a plethora of techniques exist for worst case execution time (WCET) analysis of procedural programs, there are only a handful of techniques for determining the WCRT value of synchronous programs. Most of these techniques produce overestimates and hence are unsuitable for the design of systems that are predictable while being also efficient. In this paper, we present an approach for the accurate estimation of the exact WCRT value of a synchronous program, called its tight WCRT value, using model checking. For our input specifications we have selected a synchronous C based language called PRET-C that is designed for programming Precision Timed (PRET) architectures. We then present an approach for static WCRT analysis of these programs via an intermediate format called TCCFG. This intermediate representation is then compiled to produce the input for the model checker. Experimental results that compare our approach to existing approaches demonstrate the benefits of the proposed approach. The proposed approach, while presented for PRET-C is also applicable for WCRT analysis of Esterel using simple adjustments to the generated model. The proposed approach thus paves the way for a generic approach for determining the tight WCRT value of synchronous programs at compile time

Time-predictable Chip-Multiprocessor Design

Abstract—Real-time systems need time-predictable platforms to enable static worst-case execution time (WCET) analysis. Improving the processor performance with superscalar techniques makes static WCET analysis practically impossible. However, most real-time systems are multi-threaded applications and performance can be improved by using several processor cores on a single chip. In this paper we present a time-predictable chipmultiprocessor system that aims to improve system performance while still enabling WCET analysis. The proposed chip-multiprocessor (CMP) uses a shared memory with a time-division multiple access (TDMA) based memory access scheduling. The static TDMA schedule can be integrated into the WCET analysis. Experiments with a JOP based CMP showed that the memory access starts to dominate the execution time when using more than 4 processor cores. To provide a better scalability, more local memories have to be used. We add a processor local scratchpad memory and split data caches, which are still time-predictable, to the processor cores. I

Formal and Informal Methods for Multi-Core Design Space Exploration

We propose a tool-supported methodology for design-space exploration for embedded systems. It provides means to define high-level models of applications and multi-processor architectures and evaluate the performance of different deployment (mapping, scheduling) strategies while taking uncertainty into account. We argue that this extension of the scope of formal verification is important for the viability of the domain.Comment: In Proceedings QAPL 2014, arXiv:1406.156

Towards a Time-predictable Dual-Issue Microprocessor: The Patmos Approach

Current processors are optimized for average case performance, often leading to a high worst-case execution time (WCET). Many architectural features that increase the average case performance are hard to be modeled for the WCET analysis. In this paper we present Patmos, a processor optimized for low WCET bounds rather than high average case performance. Patmos is a dual-issue, statically scheduled RISC processor. The instruction cache is organized as a method cache and the data cache is organized as a split cache in order to simplify the cache WCET analysis. To fill the dual-issue pipeline with enough useful instructions, Patmos relies on a customized compiler. The compiler also plays a central role in optimizing the application for the WCET instead of average case performance