216 research outputs found
Design of asynchronous microprocessor for power proportionality
PhD ThesisMicroprocessors continue to get exponentially cheaper for end users following Moore’s
law, while the costs involved in their design keep growing, also at an exponential rate.
The reason is the ever increasing complexity of processors, which modern EDA tools
struggle to keep up with. This makes further scaling for performance subject to a high
risk in the reliability of the system. To keep this risk low, yet improve the performance,
CPU designers try to optimise various parts of the processor. Instruction Set Architecture
(ISA) is a significant part of the whole processor design flow, whose optimal design
for a particular combination of available hardware resources and software requirements
is crucial for building processors with high performance and efficient energy utilisation.
This is a challenging task involving a lot of heuristics and high-level design decisions.
Another issue impacting CPU reliability is continuous scaling for power consumption. For
the last decades CPU designers have been mainly focused on improving performance, but
“keeping energy and power consumption in mind”. The consequence of this was a development
of energy-efficient systems, where energy was considered as a resource whose
consumption should be optimised. As CMOS technology was progressing, with feature
size decreasing and power delivered to circuit components becoming less stable, the
energy resource turned from an optimisation criterion into a constraint, sometimes a critical
one. At this point power proportionality becomes one of the most important aspects
in system design. Developing methods and techniques which will address the problem
of designing a power-proportional microprocessor, capable to adapt to varying operating
conditions (such as low or even unstable voltage levels) and application requirements in
the runtime, is one of today’s grand challenges. In this thesis this challenge is addressed
by proposing a new design flow for the development of an ISA for microprocessors, which
can be altered to suit a particular hardware platform or a specific operating mode. This
flow uses an expressive and powerful formalism for the specification of processor instruction
sets called the Conditional Partial Order Graph (CPOG). The CPOG model captures
large sets of behavioural scenarios for a microarchitectural level in a computationally
efficient form amenable to formal transformations for synthesis, verification and automated
derivation of asynchronous hardware for the CPU microcontrol. The feasibility of
the methodology, novel design flow and a number of optimisation techniques was proven
in a full size asynchronous Intel 8051 microprocessor and its demonstrator silicon. The
chip showed the ability to work in a wide range of operating voltage and environmental
conditions. Depending on application requirements and power budget our ASIC supports
several operating modes: one optimised for energy consumption and the other one for
performance. This was achieved by extending a traditional datapath structure with an
auxiliary control layer for adaptable and fault tolerant operation. These and other optimisations
resulted in a reconfigurable and adaptable implementation, which was proven
by measurements, analysis and evaluation of the chip.EPSR
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Platform as a service gateway for the Fog of Things
Internet of Things (IoT), one of the key research topics in recent years, together with concepts from Fog Computing, brings rapid advancements in Smart City, Monitoring Systems, industrial control, transportation and other fields. These applications require a reconfigurable sensor architecture that can span multiple scenarios, devices and use cases that allow storage, networking and computational resources to be efficiently used on the edge of the network. There are a number of platforms and gateway architectures that have been proposed to manage these components and enable application deployment. These approaches lack horizontal integration between multiple providers as well as higher order functionalities like load balancing and clustering. This is partly due to the strongly coupled nature of the deployed applications, a lack of abstraction of device communication layers as well as a lock-in for communication protocols. This is a major obstacle for the development of a protocol agnostic application environment that allows for single application to be migrated and to work with multiple peripheral devices with varying protocols from different local gateways. This research looks at existing platforms and their shortcomings as well as proposes a messaging based modular gateway platform that enables clustering of gateways and the abstraction of peripheral communication protocols. This allows applications to send and receive messages regardless of their location and destination device protocol, creating a more uniform development environment. Furthermore, it results in a more streamlined application development and testing while providing more efficient use of the gateways resources. Our evaluation of a prototype for the system shows the need for the migration of resources and the QoS advantages of such a system. The presented use-case scenarios show that clustering can prove to be an advantage in certain use-cases as well as the deployment of a larger testing and control environment through the platform
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