Customizing and hardwiring on-chip interconnects in FPGAs

This thesis presents our investigations on how to efficiently utilize on-chip wires to improve network performance in reconfigurable hardware. A fieldprogrammable gate array (FPGA), as a key component in a modern reconfigurable platform, accommodates many-millions of wires and the on-demand reconfigurability is realized using this abundance of wires. Modern FPGAs become computationally powerful as hardware IP (intellectual property) modules such as embedded memories, processor cores, and DSP modules are accommodated. However, the performance and the cost of the inter-IP communication remains a main challenge. We meet this challenge in two aspects. First, conventional general-purpose on-chip networks suffer from high area cost when they are mapped onto the reconfigurable fabric. To reduce the area cost, we present a topology customization technique for a given set of applications. Specifically, we present an application-specific crossbar switch, crossbar schedulers, point-to-point interconnects, and circuit-switched networks-on-chip (NoCs) that reside on top of a reconfigurable fabric. As a result, by establishing only the necessary network resources, our customized interconnects provide significantly reduced cost compared to general-purpose on-chip networks. Second, while the reconfigurability is a key benefit in FPGAs, it is traded off by decreased performance and increased cost. This is mainly because of the bit-level reconfigurable interconnects. To increase performance and reduce cost, we propose to replace the bit-level reconfigurable wires by hardwired circuit-switched interconnects for the inter-IP communication. Specifically, we present hardwired crossbars and a circuit-switched NoC interconnect fabric. We describe the advantages of the hardwired networks evidenced by the quantified performance analysis, network simulation, and an implementation. As a result, the hardwired networks provide two orders of magnitude better performance per area than the networks that are mapped onto the reconfigurable fabric.Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Design Trade-offs in Customized On-chip Crossbar Schedulers

In this paper, we present a design and an analysis of customized crossbar schedulers for reconfigurable on-chip crossbar networks. In order to alleviate the scalability problem in a conventional crossbar network, we propose adaptive schedulers on customized crossbar ports. Specifically, we present a scheduler with a weighted round robin arbitration scheme that takes into account the bandwidth requirements of specific applications. In addition, we propose the sharing of schedulers among multiple ports in order to reduce the implementation cost. The proposed schedulers arbitrate on-demand (at design time) interconnects and adhere to the link bandwidth requirements, where physical topologies are identical to logical topologies for given applications. Considering conventional crossbar schedulers as reference designs, a comparative performance analysis is conducted. The hardware scheduler modules are parameterized. Experiments with practical applications show that our custom schedulers occupy up to 83% less area, and maintain better performance compared to the reference schedulers.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Measurement of 137Cs in Ice Core Samples from Antarctica

Three different ice core samples from Antarctica were analyzed to identify activity concentrations of radioactive isotopes. Tracking migration of radioactive isotopes to Antarctica can provide a key clue to understand global environmental changes caused by radiation exposures because the Antarctic ice cores can preserve unique characteristics of various environmental conditions. We are particularly interested in the 137Cs nucleus, because it is closely related to radiation exposure from nuclear power plant accidents and nuclear bomb tests. With its half life of 30.17��0.03 years, 137Cs can also be used to assess the age of sedimentation occurring after around the year 1945. We selected three ice core samples, called Tarn8, Styx27, and H25, from different time periods; the Tarn8 sample is known to be from earlier than ~ 1000 AD, the Styx27 sample is approximately from the year 1945, and the H25 sample is from the year 2012. Radioactive isotope measurements of the ice core samples were performed using a 100% HPGe detector at Cheongpyeong Underground Radiation Laboratory (CURL). We measured the activity of 137Cs in the H25 sample to be 0.98 �� 0.82 mBq/kg. Although the activity has a large uncertainty mainly due to the limited sample quantity, the 137Cs isotopes in the Antarctic ice core were measured for the first time in Korea. (c)2018, The Korean Physical Society11Nsciescopuskc

Generation of low-order Laguerre-Gaussian beams using hybrid-machined reflective spiral phase plates for intense laser-plasma interactions

© 2020 The Author(s). In laser-plasma interactions (LPI), the laser beam mode is a critical parameter when trying to explore new physical phenomena. Of the various spatial beam modes, the Laguerre-Gaussian (LG) mode with vortex phase has attracted considerable attention due to its unique features, including the ability to carry an orbital angular momentum. Due to this, it has been actively applied to LPI, which mainly utilize ultrashort intense laser pulses. However, existing transmissive phase-manipulating optical elements have several limitations when applied in LPI due to critical issues such as pulse broadening, attenuation, and beam shape–all of which have an influence on the beam quality, as well as, geometry, size, simplicity, and cost–all of which are related to processing technologies. In this paper, we present a series of procedures to obtain high-quality low-order (l = 1 and 2) LG vortex beams from large-sized off-axis reflective spiral phase plates (ORSPPs). The geometric designs for various surface structures, electromagnetic wave simulations in the extra-large domain, hybrid-mechanical processing technique attempted newly, and experimental demonstrations are involved. Experimental observations of LG intensity distributions and interference fringes were verified with the simulation results of Poynting vector, phase, and angular momentum densities. The beam quality of LG intensity distributions was analyzed quantitatively through the investigation of an annular zone formed from the uniformity of the stepped and continuous surface structures of ORSPPs. Furthermore, we numerically investigated the physical phenomena on the high-intensity angular momentum transfer from light to matter, considering ORSPP–driven low-order LG vortex laser pulses, by performing 3D particle-in-cell simulations11Nsci