Tommi Zetterman

Variable length instruction compression on Transport Triggered Architectures

The memories used for embedded microprocessor devices consume a large portion of the system’s power. The power dissipation of the instruction memory can be reduced by using code compression methods, which may require the use of variable length instruction formats in the processor. The power-efficient design of variable length instruction fetch and decode is challenging for static multiple-issue processors, which aim for low power consumption on embedded platforms. The memory-side power savings using compression are easily lost on inefficient fetch unit design. We propose an implementation for instruction template-based compression and two instruction fetch alternatives for variable length instruction encoding on transport triggered architecture, a static multiple-issue exposed data path architecture. With applications from the CHStone benchmark suite, the compression approach reaches an average compression ratio of 44% at best. We show that the variable length fetch designs reduce the number of memory accesses and often allow the use of a smaller memory component. The proposed compression scheme reduced the energy consumption of synthesized benchmark processors by 15% and area by 33% on average.

Turbo decoding on tailored OpenCL processor

Turbo coding is commonly used in the current wireless standards such as 3G and 4G. However, due to the high computational requirements, its software-defined implementation is challenging. This paper proposes a static multi-issue exposed datapath processor design tailored for turbo decoding. In order to utilize the parallel processor datapath efficiently without resorting to low level assembly programming, the turbo decoder is implemented using OpenCL, a parallel programming standard for heterogeneous devices. The proposed implementation includes only a small set of Turbo-specific custom operations to accelerate the most critical parts of the algorithm. Most of the computation is performed using general-purpose integer operations. Thus, the processor design can be used as a general-purpose OpenCL accelerator for arbitrary integer workloads as well. The proposed processor design was evaluated both by implementing it using a Xilinx Virtex 6 FPGA and by ASIC synthesis using 130 nm and 40 nm technology libraries. The implementation achieves over 63 Mbps Turbo decoding throughput on a single low-power core. According to the ASIC synthesis, the maximum operating clock frequency is 344 MHz/1 050 MHz (130 nm/40 nm).

A Reconfigurable Multi-standard Radio Platform

This paper presents a dynamically reconfigurable multiradio RF architecture concept, which can be used for RF platform and control optimization. The platform realization is based on the RF hardware and its configuration mechanisms. The related control software is realized through functional separation of configuration management and timing control. Both key HW and SW elements are discussed and optimization opportunities evaluated using high level analysis on key building blocks.

Variable Length Instruction Compression on Transport Triggered Architectures

The memories used for embedded microprocessor devices consume a large portion of the system’s power. The power dissipation of the instruction memory can be reduced by using code compression methods, which may require the use of variable length instruction formats in the processor. The power-efficient design of variable length instruction fetch and decode is challenging for static multiple-issue processors, which aim for low power consumption on embedded platforms. The memory-side power savings using compression are easily lost on inefficient fetch unit design. We propose an implementation for instruction template-based compression and two instruction fetch alternatives for variable length instruction encoding on transport triggered architecture, a static multiple-issue exposed data path architecture. With applications from the CHStone benchmark suite, the compression approach reaches an average compression ratio of 44% at best. We show that the variable length fetch designs reduce the number of memory accesses and often allow the use of a smaller memory component. The proposed compression scheme reduced the energy consumption of synthesized benchmark processors by 15% and area by 33% on average.

Power optimizations for transport triggered SIMD processors

Power consumption in modern processor design is a key aspect. Optimizing the processor for power leads to direct savings in battery energy consumption in case of mobile devices. At the same time, many mobile applications demand high computational performance. In case of large scale computing, low power compute devices help in thermal design and in reducing the electricity bill. This paper presents a case study of a customized low power vector processor design that was synthesized on a 28 nm process technology. The processor has a programmer exposed datapath based on the transport triggered architecture programming model. The papers focus is on the RTL and microarchitecture level power optimizations applied to the design. Using semiautomated interconnection network and register file optimization algorithm, up to 27% of power savings were achieved. Using this as a baseline and applying register file datapath gating, register file banking and enabling clock gating of individual pipeline stages in pipelined function units, up to 26% of power and energy savings could be achieved with only a 3% area overhead. On top of this, for the measured radio applications, the exposed datapath architecture helped to achieve approximately 18% power improvement in comparison to a VLIW-like architecture by utilizing optimizations unique to transport triggered architectures.

Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering

This paper presents a dynamically reconfigurable multiradio RF architecture concept, which can be used for RF platform and control optimization. The platform realization is based on the RF hardware and its configuration mechanisms. The related control software is realized through functional separation of configuration management and timing control. Both key HW and SW elements are discussed and optimization opportunities evaluated using high level analysis on key building blocks.