This paper provides an introductory overview of the Cell multiprocessor. Cell represents a revolutionary extension of conventional microprocessor architecture and organization. The paper discusses the history of the project, the program objectives and challenges, the disign concept, the architecture and programming models, and the implementation.

Introduction to the cell multiprocessor

Magnetic flux can penetrate a type-II superconductor in the form of Abrikosov vortices (also called flux lines, flux tubes, or fluxons) each carrying a quantum of magnetic flux phi 0=h/2e. These tiny vortices of supercurrent tend to arrange themselves in a triangular flux-line lattice (FLL), which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-Tc superconductors (HTSCs) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSCs the FLL is very soft mainly because of the large magnetic penetration depth lambda . The shear modulus of the FLL is c66~1/ lambda 2, and the tilt modulus c44(k)~(1+k2 lambda 2)-1 is dispersive and becomes very small for short distortion wavelengths 2 pi /k<< lambda . This softness is enhanced further by the pronounced anisotropy and layered structure of HTSCs, which strongly increases the penetration depth for currents along the c axis of these (nearly uniaxial) crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may `melt` the FLL and cause thermally activated depinning of the flux lines or ofthe two-dimensional `pancake vortices` in the layers. Various phase transitions are predicted for the FLL in layered HTSCs. Although large pinning forces and high critical currents have been achieved, the small depinning energy so far prevents the application of HTSCs as conductors at high temperatures except in cases when the applied current and the surrounding magnetic field are small.

https://iopscience.iop.org/article/10.1088/0034-4885/58/11/003/pdf

The flux-line lattice in superconductors

The nature and length scales of charge screening in complex oxides are fundamental to a wide range of systems, spanning ceramic voltage-dependent resistors (varistors), oxide tunnel junctions and charge ordering in mixed-valence compounds. There are wide variations in the degree of charge disproportionation, length scale, and orientation in the mixed-valence compounds: these have been the subject of intense theoretical study, but little is known about the microscopic electronic structure. Here we have fabricated an idealized structure to examine these issues by growing atomically abrupt layers of LaTi(3+)O(3) embedded in SrTi(4+)O(3). Using an atomic-scale electron beam, we have observed the spatial distribution of the extra electron on the titanium sites. This distribution results in metallic conductivity, even though the superlattice structure is based on two insulators. Despite the chemical abruptness of the interfaces, we find that a minimum thickness of five LaTiO(3) layers is required for the centre titanium site to recover bulk-like electronic properties. This represents a framework within which the short-length-scale electronic response can be probed and incorporated in thin-film oxide heterostructures.

Artificial charge-modulationin atomic-scale perovskite titanate superlattices

Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices. These tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-$T_c$ supercon- ductors (HTSC's) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft mainly because of the large magnetic penetration depth: The shear modulus of the FLL is thus small and the tilt modulus is dispersive and becomes very small for short distortion wavelength. This softness of the FLL is enhanced further by the pronounced anisotropy and layered structure of HTSC's, which strongly increases the penetration depth for currents along the c-axis of these uniaxial crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause thermally activated depinning of the flux lines or of the 2D pancake vortices in the layers. Various phase transitions are predicted for the FLL in layered HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to interesting effects which strongly depend on the geometry of the experiment.

The Flux-Line Lattice in Superconductors

Recent studies on high-Tc superconductors have aroused new interest in tunnelling effects in unconventional superconductors. Unlike in conventional s-wave superconductors, the d-wave pairing state in these materials has an internal phase of the pair potential. The internal phase as a function of the wavevector of the Cooper pairs has a large influence on the electric properties of tunnelling junctions. Important effects of the internal phase on the Josephson current were first predicted theoretically. The idea has been established through several experiments using high-Tc Josephson junctions, which detect ?-phase shift between the a- and b-axis directions and fractional flux quanta. These results give convincing evidence for d-wave symmetry in high-Tc superconductors. In addition, the existence of new interference effects in the quasiparticle states near surfaces and boundaries has been suggested through theoretical predictions. Experimentally, a large number of tunnelling spectroscopy data showed zero-bias conductance peaks (ZBCPs), the origin of which cannot be explained in terms of the classical concept that a tunnelling conductance spectrum is a phase-insensitive probe of the electronic states. It is clarified theoretically that the observed ZBCPs reflect the formation of zero-energy states on the surface due to the ?-phase shift of internal phase in the d-wave pairing symmetry. The formulation developed for tunnelling spectroscopy suggests that tunnelling spectroscopy is essentially phase sensitive. In addition, the formation of the bound states has been shown to have a serious influence on the electrical properties of Josephson junctions. Several anomalous properties including strong enhancement of the Josephson current in the low-temperature region have been predicted theoretically. In this report, recent developments in tunnelling effects on surface bound states in unconventional superconductors are reviewed.

https://iopscience.iop.org/article/10.1088/0034-4885/63/10/202/pdf

Tunnelling effects on surface bound states in unconventional superconductors

Thin film superconductors of the YBaCuO family have been fabricated using layer structures of Cu/BaO/Y 2 O 3 deposited by electron-beam evaporation Using layer thicknesses off the stoichiometric YBa 2 Cu 3 O 7 , we have formed superconducting films with zero resistance above 77°K using MgO and SrTiO 3 substrates The films were found to be composed of both the superconducting YBa 2 Cu 3 O 7 phase, and the non-superconducting green Y 2 BaCuO 7 phase Dependence of transition temperatures on the annealing temperatures and the substrates has also been studied

Formation of thin film YBaCuO Superconductors from Cu/BaO/Y2O3 Layer Structures

A system and method for enabling the estimation and mitigation of self-heating in chip designs at a much earlier stage in a design flow. The system and method provides unique characterization of each standard cell in a library for its effective thermal resistance based on the topology and layout of the cell, and brings this per standard cell instance based delta-T to be available for the timing closure tools when completing a synthesized design. Thus, at the timing closure process, the generated design is free of self heating violations. The method computes a unique thermal resistance characterization on per standard cell manner—based on the topology, function and layout of the standard cell, and uses that to compute the deltaT per instance of the design. This information is presented to a violation mitigation tool which changes the power levels of the cells, logic function to mitigate the self heating violations.

Early analysis and mitigation of self-heating in design flows

Verfahren zur Vorbehandlung von Kunststoffsubstraten.

An electrical signal sampling probe apparatus to determine the response of electrical circuits or devices to ultrafast electrical pulses. The probe is detachable from the device being tested. The probe includes a transparent substrate (10) though which optical pulses are focused or directed onto a photo­conducting gap (12). The probe further includes a transmission line (18, 20) associated with the photo­conductive gap, and which terminates at a tapered end of the probe in contacts (22) which are placed on the device under test.

Electrical signal sampling probe apparatus

The effect of uniaxial strain e on superconducting transition temperature T c of thin YBa 2 Cu 3 O 7 film is presented. The value of T C increases linearly with compressional strain with a slope of -275K/e. Under tensile strain, T c initially decreases to a value ∼ 0.3K below the zero-strain value and then remains constant with additional strain. In compression, the logarithmic strain derivative of T c , (1/T c )(dT c /de), is -3 per unit strain which is slightly less than 4–6 per unit strain observed in conventional superconductors.

Michael R. Scheuermann

Papers

Formation of thin film YBaCuO Superconductors from Cu/BaO/Y2O3 Layer Structures

Early analysis and mitigation of self-heating in design flows

Verfahren zur Vorbehandlung von Kunststoffsubstraten.

Electrical signal sampling probe apparatus

Effect of Uniaxial Strain on the Superconducting Transition Temperature in thin YBa2Cu3O7 Film