Channel Characterization for Chip-scale Wireless Communications within Computing Packages

Wireless Network-on-Chip (WNoC) appears as a promising alternative to conventional interconnect fabrics for chip-scale communications. WNoC takes advantage of an overlaid network composed by a set of millimeter-wave antennas to reduce latency and increase throughput in the communication between cores. Similarly, wireless inter-chip communication has been also proposed to improve the information transfer between processors, memory, and accelerators in multi-chip settings. However, the wireless channel remains largely unknown in both scenarios, especially in the presence of realistic chip packages. This work addresses the issue by accurately modeling flip-chip packages and investigating the propagation both its interior and its surroundings. Through parametric studies, package configurations that minimize path loss are obtained and the trade-offs observed when applying such optimizations are discussed. Single-chip and multi-chip architectures are compared in terms of the path loss exponent, confirming that the amount of bulk silicon found in the pathway between transmitter and receiver is the main determinant of losses.Comment: To be presented 12th IEEE/ACM International Symposium on Networks-on-Chip (NOCS 2018); Torino, Italy; October 201

An Electromigration and Thermal Model of Power Wires for a Priori High-Level Reliability Prediction

In this paper, a simple power-distribution electrothermal model including the interconnect self-heating is used together with a statistical model of average and rms currents of functional blocks and a high-level model of fanout distribution and interconnect wirelength. Following the 2001 SIA roadmap projections, we are able to predict a priori that the minimum width that satisfies the electromigration constraints does not scale like the minimum metal pitch in future technology nodes. As a consequence, the percentage of chip area covered by power lines is expected to increase at the expense of wiring resources unless proper countermeasures are taken. Some possible solutions are proposed in the paper

Experimental investigation of open-ended microwave oven assisted encapsulation process

An open ended microwave oven is presented with improved uniform heating, heating rates and power conversion efficiency. This next generation oven produces more uniform EM fields in the evanescent region forming part of the heating area of the oven. These fields are vital for the rapid and uniform heating of various electromagnetically lossy materials. A fibre optic temperature sensor and an IR pyrometer are used to measure in situ and in real-time the temperature of the curing materials. An automatic computer controlled closed feedback loop measures the temperature in the curing material and drives the microwave components to obtain predetermined curing temperature cycles for efficient curing. Uniform curing of the lossy encapsulants is achieved with this oven with typical cure cycle of 270 seconds with a ramp rate of 1oC/s and a hold period of 2 minutes. Differential scanning calorimeter based measurement for the pulsed microwave based curing of the polymer dielectric indicates a ~ 100% degree of cure

A New Approach to Speeding Up Topic Modeling

Latent Dirichlet allocation (LDA) is a widely-used probabilistic topic modeling paradigm, and recently finds many applications in computer vision and computational biology. In this paper, we propose a fast and accurate batch algorithm, active belief propagation (ABP), for training LDA. Usually batch LDA algorithms require repeated scanning of the entire corpus and searching the complete topic space. To process massive corpora having a large number of topics, the training iteration of batch LDA algorithms is often inefficient and time-consuming. To accelerate the training speed, ABP actively scans the subset of corpus and searches the subset of topic space for topic modeling, therefore saves enormous training time in each iteration. To ensure accuracy, ABP selects only those documents and topics that contribute to the largest residuals within the residual belief propagation (RBP) framework. On four real-world corpora, ABP performs around $10$ to $100$ times faster than state-of-the-art batch LDA algorithms with a comparable topic modeling accuracy.Comment: 14 pages, 12 figure

Millimeter-wave propagation within a computer chip package

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Wireless Network-on-Chip (WNoC) appears as a promising alternative to conventional interconnect fabrics for chip-scale communications. The WNoC paradigm has been extensively analyzed from the physical, network and architecture perspectives assuming mmWave band operation. However, there has not been a comprehensive study at this band for realistic chip packages and, thus, the characteristics of such wireless channel remain not fully understood. This work addresses this issue by accurately modeling a flip-chip package and investigating the wave propagation inside it. Through parametric studies, a locally optimal configuration for 60 GHz WNoC is obtained, showing that chip-wide attenuation below 32.6 dB could be achieved with standard processes. Finally, the applicability of the methodology is discussed for higher bands and other integrated environments such as a Software-Defined Metamaterial (SDM).Peer ReviewedPostprint (author's final draft