73 research outputs found
Through Silicon Via-Based Grid for Thermal Control in 3D Chips
3D stacked chips have become a promising integration technology for modern systems. The complexity reached in multi-processor systems has increased the communication delays between processing cores, and an effective way to diminish this impact on communication is the 3D integration technology and the use of through-silicon vias (TSVs) for inter-layer communication. However, 3D chips present important ther- mal issues due to the presence of processing units with a high power density, which are not homogeneously distributed in the stack. Also, the presence of hot-spots creates thermal gradients that impact negatively on the system reliability and relate with the leakage power consumption. Thus, new approaches for thermal control of 3D chips are in great need. This paper discusses the use of a grid and non-uniform placement of TSVs as an effective mechanism for thermal balancing and control in 3D chips. We have modelled the material layers and TSVs mathematically using a detailed calibration phase based on a real 5-tier 3D chip stack, where several heaters and sensors are manufactured to study the heat diffusion. The obtained results show interesting conclusions about thermal dissipation for 3D chips with TSVs and outline new insights in the area of thermal modeling and optimization for 3D chips by exploiting the inclusion of minimal percentages of TSVs in strategic positions of the layout
High Speed Cycle-Approximate Simulation of Embedded Cache-Incoherent and Coherent Chip-Multiprocessors
HW-SW Emulation Framework for Temperature-Aware Design in MPSoCs
New tendencies envisage Multi-Processor Systems-On-Chip (MPSoCs) as a promising solution for the consumer electronics market. MPSoCs are complex to design, as they must execute multiple applications (games, video), while meeting additional design constraints (energy consumption, time-to-market). Moreover, the rise of temperature in the die for MPSoCs can seriously affect their final performance and reliability. In this paper, we present a new hardware-software emulation framework that allows designers a complete exploration of the thermal behavior of final MPSoC designs early in the design flow. The proposed framework uses FPGA emulation as the key element to model the hardware components of the considered MPSoC platform at multi-megahertz speeds. It automatically extracts detailed system statistics that are used as input to our software thermal library running in a host computer. This library calculates at run-time the temperature of on-chip components, based on the collected statistics from the emulated system and the final floorplan of the MPSoC. This enables fast testing of various thermal management techniques. Our results show speed-ups of three orders of magnitude compared to cycle-accurate MPSoC simulator
Back-reaction instabilities of relativistic cosmic rays
We explore streaming instabilities of the electron-ion plasma with
relativistic and ultra-relativistic cosmic rays in the background magnetic
field in the multi-fluid approach. Cosmic rays can be both electrons and ions.
The drift speed of cosmic rays is directed along the magnetic field. In
equilibrium, the return current of the background plasma is taken into account.
One-dimensional perturbations parallel to the magnetic field are considered.
The dispersion relations are derived for transverse and longitudinal
perturbations. It is shown that the back-reaction of magnetized cosmic rays
generates new instabilities one of which has the growth rate that can approach
the growth rate of the Bell instability. These new instabilities can be
stronger than the cyclotron resonance instability. For unmagnetized cosmic
rays, the growth rate is analogous to the Bell one. We compare two models of
the plasma return current in equilibrium with three and four charged
components. Some difference between these models is demonstrated. For
longitudinal perturbations, an instability is found in the case of
ultra-relativistic cosmic rays. The results obtained can be applied to
investigation of astrophysical objects such as the shocks by supernova
remnants, galaxy clusters, intracluster medium and so on, where interaction of
cosmic rays with turbulence of the electron-ion plasma produced by them is of a
great importance for the cosmic-ray evolution.Comment: Accepted for publication in Plasma Physics and Controlled Fusio
A Flexible Simulation Framework for Graphics Architectures
In this paper we describe a multipurpose tool for analysis of the performance characteristics of computer graphics hardware and software. We are developing Qsilver, a highly configurable micro-architectural simulator of the GPU that uses the Chromium system's ability to intercept and redirect an OpenGL stream. The simulator produces an annotated trace of graphics commands using Chromium, then runs the trace through a cycle-timer model to evaluate time-dependent behaviors of the various functional units. We demonstrate the use of Qsilver on a simple hypothetical architecture to analyze performance bottlenecks, to explore new GPU microarchitectures, and to model power and leakage properties. One innovation we explore is the use of dynamic voltage scaling across multiple clock domains to achieve significant energy savings at almost negligible performance cost
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