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About This Issue
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Silicon Laser and Cell Processor
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Feruary 28 - March 4, 2005 By Dr. Jack Horgan
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Read business product alliance news and analysis of weekly happenings
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Introduction
In the past few weeks there have been two announcement of technical significance. On February 17, 2005 Intel published an article in the prestigious scientific journal Nature disclosing the development of the first continuous wave all-silicon laser on a single silicon chip using the Raman effect. On February 7, 2005 IBM, Sony Group and Toshiba announced at the International Solid State Circuit Conference (ISSOC) their jointly developed microprocessor code-named Cell.
In general when such announcements are made, it does not mean that one can rush down to the corner store and buy one. Considerable time may elapse before these discoveries become part of any commercial offerings. Why then do firms make these technical achievement announcements? Sometimes they are made as an "atta boy" of appreciation for the people involved, to promote the firm with existing and prospective customers and shareholders and to scare off potential competitors in the same way that patent pending notices do. Firms like IBM and Intel have significant research operations who publish their findings in respected journals just like University professors.
Silicon Laser
Intel's announcement on the continuous wave laser was a rapid follow up to earlier papers. The silicon photonics research team has achieved a number of breakthroughs, starting in 2004 with the first silicon-based optical modulator to encode data at 1GHz, an increase of over 50 times the previous research record of about 20MHz. In October 2004 Drs. Ozdal Boyraz and Bahram Jalali of the University of California Los Angeles reported the first demonstration of a pulsed silicon Raman laser in Optics Express. Haisheng Rong was the lead researcher at Intel.
Building a Raman laser in silicon begins with etching a waveguide, a conduit for light on a chip. Silicon is transparent to infrared light so that when light is directed into a waveguide it can be contained and channelled across a chip. An external light source is used to 'pump' light into its chip. As light is pumped in, the natural atomic vibrations in silicon amplify the light as it passes through the chip due to the Raman effect. Because of its crystalline structure, silicon atoms readily vibrate when hit with light and the resulting Raman effect is more than 10,000 times stronger in silicon than in glass fibres.
Raman lasers and amplifiers are used today in the telecoms industry and rely on miles of fibre to amplify light. By using silicon, Intel said it could achieve similar results using a silicon chip just a few centimetres in size.
Dr. Mario Paniccia, director, Intel's Photonics Technology Lab., said about the announcement that "Fundamentally, we have demonstrated for the first time that standard silicon can be used to build devices that amplify light. The use of high-quality photonic devices has been limited because they are expensive to manufacture, assemble and package. This research is a major step toward bringing the benefits of low-cost, high-bandwidth silicon based optical devices to the mass market." This brings Intel closer to realizing its vision of "siliconizing" photonics. In the past lasers that drive optical communications have been made of more exotic materials such as indium phosphide (InP)
and gallium arsenide (GaAs).
What is attractive about the silicon laser is that semiconductor fabs have considerable investment in and experience with making semiconductors. The demand for semiconductors is cyclic leading to boom and bust stages. Using the facilities for a different application would help even out capacity utilization.
Laser Background
The term laser stands for light amplification by stimulated emission of radiation. The basic components of a laser are a medium and a cavity or housing to contain the medium. The medium can be a solid, gas, liquid or semiconductor. Let us look at the basic mechanism of a ruby laser, the first laser that was invented in 1960. Ruby (CrAlO3) is an aluminum oxide crystal in which some of the aluminum atoms have been replaced with chromium atoms. Chromium gives ruby its characteristic red color and is responsible for the lasing behavior of the crystal.
An electron is typically found in its ground state but can be raised to one or more higher specific energy levels or quantum levels by a variety of means. The electron will in a small fraction of a second return to its ground state or cascaded down the energy levels to the ground state by giving up the difference in energy levels as electromagnetic energy in the form of a photon. This is spontaneous emission. The possible energy levels differ from atom to atom. In fact this mechanism is the basis of atomic spectroscopy that identifies the presence of various elements in a sample. If many electrons or molecules in the case of some lasers could be excited creating an inversion population
of excited versus unexcited electrons, then the possibility arises of creating a laser beam. This process is sometimes referred to as "pumping". The spontaneously emitted photon however will go in all directions and are not be "in step". Laser light is monochromatic, directional and coherent. If one of these spontaneous photons passes by an electron in an excited state, it stimulates the electron to give off its energy in the form of a photon that is in phase, in the same direction and of the same wavelength and frequency as the original photon. As these two photons move through the medium they can stimulate additional emissions with the same properties. If the cavity has mirrors at
both ends, these photons can pass back and forth through the medium stimulating more and more photons thereby amplifying the light intensity. If one of the mirrors is only partially reflecting, the coherent laser beam can escape. Unlike a flashlight beam this coherency property prevents the beam from spreading out.
In the case of the early ruby laser, a cylindrical crystal of ruby was used. A high-intensity lamp spiraled around the ruby cylinder provided a flash of white light that triggers population inversion. The ruby laser is a three-level laser and therefore is somewhat more complicated than described above. Light in the green and blue regions of the spectrum is absorbed by chromium ions, raising the energy of electrons of the ions from the ground state level to a broad band of levels which rapidly undergo non-radiative transitions to the two metastable levels. In this case of non-radiative transition the energy released in the transition is dissipated as heat in the ruby crystal. The
metastable levels are unusual in that they have a relatively long lifetime of about 4 milliseconds which aids the creation of an inversion population. The process now proceeds as describe above emitting red light of wavelength 694.3 nm.
Lasers differ in the medium used, the method to activate and the frequency and wavelength of the emitted beam. Frequency, wavelength and energy of electromagnetic waves are related by the well known formulas
λ = c/f and E = hc/ λ
where
E is energy measured in ergs
c is the speed of light in a vacuum, 29,979,245,800 centimeters per second
f is the frequency of light measured in cycles per seconds or Hertz
λ is the wavelength of light measured in centimeters. The wavelength of light is often presented in terms of Angstroms (10-10 meters)
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The wavelength of the laser beam determines the range of applications and degree of potential danger to humans.
Laser are routinely used in consumer products (printers, scanners, CD, DVD, ..), medicine (dental, eye and cosmetic surgery), military (guidance, navigation, ..), industry (cutting, annealing, …)
Raman Effect
When light is scattered by a molecular system, most of the scattering is elastic or Raleigh scattering where the emitted photon has the same wavelength as the absorbing photon from the incident light. However, a small fraction of the scattering is inelastic, an effect discovered by Indian physicist C. V. Raman in 1928. In Raman scattering, the energies of the incident and scattered photons are different. The energy and thus the frequency and wavelength of the scattered light is changed as the light either imparts energy to the scattering molecules or takes energy away. If one measures the scattered light as function of wavelength most will be found to have the original wavelength of the
incident radiation and a much smaller portions will be found corresponding to the shorter or longer wavelengths of the altered portion of the light. This Raman spectrum is characteristic of the transmitting substance and thus can be used as a basis for spectroscopy. If the initial beam is sufficiently intense and monochromatic, a threshold can be reached beyond which light at the Raman frequencies is amplified, builds up strongly, and generally exhibits the characteristics of stimulated emission.
The Raman effect is widely used today to make amplifiers and lasers in glass fiber. However, fiber-based devices using the Raman effect are limited because they require kilometers of fiber to provide sufficient amplification. The Raman effect is more than 10,000 times stronger in silicon than in glass optical fiber, making silicon an advantageous material. Instead of kilometers of fiber, only centimeters of silicon are required.
The fabrication of a silicon laser begins with the creation of a waveguide by etching a ridge or channel into a silicon wafer. Light pumped into this waveguide will be contained and channeled across the chip. In any waveguide there is a loss of light due to a variety of factors. Intel researchers discovered that that increasing the pump power beyond a certain point no longer increased the amplification and eventually even decreased it. This reduction was due to so-called two-photon absorption process. It is possible for two photons to arrive at an atom at the same time in such a way that the combined energy is enough to free an electron from an atom. These free electrons build up over
time and absorb some of the light passing through the silicon waveguide thereby canceling out the Raman amplification.
Intel's solution was to change the design of the waveguide by embedding it within a semiconductor device, a reverse-biased p-i-n (P-type - Intrinsic - N-type) junction diode. It is formed by implanting a short region on each side of the waveguide with impurities that convert silicon into a material with electron (n-side) or hole (p-side) conduction. When a voltage is applied to this device, it acts like a vacuum and removes the electrons from the path of the light.
The silicon laser could lead to many applications including optical amplifiers, wavelength converters, and various types of lasers in silicon. Optical communications and silicon photonic technology will allow enterprises to scale bandwidth availability to meet the needs of network infrastructure.
Cell Processor
In November 2004 IBM, Sony, Sony Computer Entertainment and Toshiba first unveiled some of the key concepts of their Cell processor, the result of a four-year collaborative effort. At that time Boris Petrov, managing partner of the research firm Petrov Group, commented that "The year 2004 marks the birth of a distinctly new cellular computing era. As with past watershed computing events, the driving and trend-setting force will be IBM. While I shy away from hyperbole, our report demonstrates that the business impact of IBM's new cellular computing technology will be potentially as profound as the Yucatan asteroid's was on life on Earth millions of years ago." What marketing manager
would not give his soul for a quote like that? Masayuki Chatani, corporate executive and CTO, Sony computer Entertainment Inc, was a tad more restrained when he said that "The Cell processor-based workstation will totally change the digital content creation environment. Its overwhelming power will be demonstrated in every aspect of the development of all kinds of digital entertainment content, from movies, broadcast programs to next generation PlayStation games."
This level of hype is obviously quite a lot to live up to. Sony intends to use the Cell chip in its Sony's PlayStation 3 video console as well as in home servers and high definition television (HDTV) in 2006, Toshiba plans to use the Cell in digital television sets and IBM intends to put it in computer servers and work stations. The fact that all three firms involved will incorporate the Cell chip in mass market products (Sony PlayStation2 sold 89 million units by the end of 2004) will help ensure its success.
The press releases did not go into very much detail. Some technical analysts have poured over the patent application in order to ferret out some of the technical nuggets.
The Cell chip will have 234 million transistors, measures 221mm2 and be produced using advanced 90nm silicon-on-insulator (SOI) processes.
Among the highlights of Cell processor:
- Cell is a breakthrough architectural design -- featuring eight synergistic processors and top clock speeds of greater than 4 GHz (according to hardware tests)
- Cell is a multicore chip capable of massive floating point processing at 256 gigaflops
- Cell is OS neutral and supports multiple operating systems simultaneously including real-time consumer electronics and game console operating systems.
- Resource management system for real-time applications
- On-chip hardware in support of security system for intellectual property protection
- 6.4 Gigabit / second off-chip communication
- 2.5 MB on-chip memory (512KB L2 and 8*256KB)
- Autonomic power management
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The Cell is an asymmetric design with two types of processors. A 64-bit RISC PowerPC processor acts as a PPE (Primary Processing Element). The main cell processor supports dual-threaded (SMT) operation, using a 32KB L1 cache and a 512KB level 2 cache. There are also eight sub or helper 32-bit units acting as SPEs (Synergistic Processing Elements). Each of these "cells" has 256KB of private Load Store (LS) memory, a 4 x 128 bit ALU's (Arithmetic Logical Unit), and 128 x 128 bit registers. These vector processors serve as standalone Alternate or Attached Processing Units (APUs) executing APUlets. The APUs operate on registers which are read from or written to the local memory. This local
memory can access main memory in blocks of 1024 bits.
The SPE's can be chained together in a steaming mode. The system accepts data and processes it in a series of steps that can be
performed by one or more SPEs. Data is read into the local memory of one unit, processed and written to RAM accessible by other SPE units.
The SPEs are connected to each other and to a 512KB L2 cache via an Element Interface Bus (EIB) that consists of four 128-bit wide data channels. The individual SPEs can use this bus to communicate with each other, and this includes the transfer of data in between SPEs acting as peers on the network. The SPEs also communicate with the L2 cache, with main memory via the memory interface controller (MIC)
According to Rambus, Inc the Cell processor incorporates Rambus's XDR memory and FlexIO processor bus interface solutions. The memory and processor bus interfaces designed by Rambus account for 90% of the Cell processor signal pins, providing an aggregate processor I/O bandwidth of approximately 100 gigabytes-per-second. The Rambus XDR (eXtreme Data Rate) memory interface is capable of data rates of 3.2GHz to 8.0GHz. FlexIO processor buses, formerly codenamed Redwood, are capable of running up to 6.4GHz data rates. FlexIO interfaces provide a low-latency and low-power solution for high-volume, low-cost applications, including processor, chipset and network chip connections for a broad
range of applications. FlexIO employs DRSL (Differential Rambus Signaling Level) with LVDS (Low Voltage Differential Signaling). Sony and Toshiba signed a licensing agreement with Rambus in January 2003.
The architecture is optimized for compute-intensive workloads and broadband rich media applications, including computer entertainment, movies and other forms of digital content.
The processing power of 256 gigaflops is truly impressive but would not land this "supercomputer on a chip" on the current list of the Top 500 Supercomputers.
Some have raised issues about the fact that the Cell may have to be air cooled and that it uses relatively expensive memory. This could be an impediment for some applications that typically run on inexpensive hand-held devices.
Weekly Highlights
EDA News
Cadence President and Chief Executive Officer, Mike Fister, to Present at the Morgan Stanley Semiconductor & Systems Conference
Nassda Participates on DATE 2005 Panel in Munich
Nascentric Participates in OCP-IP Panel on EDA Technology
Cadence Design Systems Selects Opsware for Global IT Automation; Billion Dollar Supplier of Electronic Design Technologies to Use Opsware Automation Across Development Environments
Pulsic Opens New Headquarters For US Territory; Appointment of New Team Signals Commitment to US Market
Cadence Senior Vice President and Chief Financial Officer, Bill Porter, to Present at the Deutsche Bank Securities Global Software Conference
Nascentric Joins OCP-IP
Cadence Sr. VP Marketing, Ajay Malhotra, and Director Investor Relations, Alan Lindstrom, to Present at the D.A. Davidson Silicon Technology Conference
OCP-IP Hosts Conference Within a Conference at DATE
Advisory/Accellera Hosts Free Luncheon Workshops & Open Member Meeting at DATE
Zuken enhances US structure, adds to executive management team and strengthens global support
Mentor Graphics Announces Tight Synthesis Integration with Xilinx ISE 7.1i and Support for Spartan-3E FPGAs
OCP-IP Announces Release of OCP 2.1 Specification
Cadence and Verisity Announce Expiration of Hart-Scott-Rodino Waiting Period
Synopsys Chief Financial Officer to Speak at the Morgan Stanley Semiconductor & Systems Conference on March 9, 2005
Grace Semiconductor Manufacturing Standardizes on Synopsys' DFM Tool Suite to Reduce GDSII-to-Mask Turnaround Time
Accelerated Technology's Nucleus EDGE Embedded Development Environment Supports Eclipse 3.0 Platform
Mentor Graphics Collaborates with VIA to Deliver PCB Reference Designs for Leading Microprocessor Suppliers
Synopsys and Hitachi Demonstrate 3Gb/s SATA II Interoperability Between DesignWare SATA Host IP Core and Deskstar Hard Drive
Cadence Invites You to Participate in the Cadence 2005 Investor & Analyst Conference Webcast
Zuken announces P-CAD to CADSTAR migration tool as part of ongoing commitment to reduce costs associated with the transition from legacy EDA packages
VaST Systems Releases Peripheral Device Builder, Next in Line of Powerful "Constructor" Tools; Peripheral Device Builder Cuts Peripheral Model Creation Time by as Much as 75%
VaST Announces CoMET 5.7; Electronic System Level Environment for Creation of Virtual System Prototypes
Cadence and Virage Logic Collaborate to Deliver Timing and Signal Integrity Views to Enable Low-Power Design
Synopsys Chief Financial Officer to Speak at the Deutsche Bank Securities Global Software Conference on March 8, 2005
ARM and Synopsys Announce Industry-First and Recommended Flow for ARM11 Family With Intelligent Energy Manager Technology
TriQuint Deploys AWR EDA Software in Design Centers; Microwave Office and VSS Design Suites To Be Used for Continuous Design Process Improvement in MMIC Products
Novas Extends Industry-Standard Debug Platform for Embedded Processor-Based System-on-Chip Designs
SpiraTech, Novas Collaborate to Deliver Powerful Transaction-Based Debug Solution
IP & SoC News
OCP Introduces 1.3 micron VCSEL-Based Gigabit Ethernet Pluggable Transceivers Capable of 2km Transmission over Legacy Multimode Fiber
Altera's PCI Express IP Core Passes PCI-SIG February Workshop Compliance Tests
First RapidIO Reference Book Released; AMCC's Sam Fuller Authors, "RapidIO-The Embedded System Interconnect"
Adveda's Univers Multi-Core Software IDE and HW/SW Co-Verification Tool Supports Altera's Nios II Embedded Processor
ON Semiconductor Expands GigaComm Portfolio to Provide a Complete Silicon Germanium Current Mode Logic Solution
Dan McCranie to Join Cypress Board of Directors; Industry Veteran and Former Cypress Executive to Replace John C. Lewis as a Member of the Cypress Board
TI Introduces Industry's Smallest LVPECL/LVDS Oscillator Buffers
Global Semiconductor Sales Show Modest Sequential Decline In January
Fifth Generation PortalPlayer SoC Triples MP3 Player Battery Life
Hitachi First to Develop Intel Itanium 2 Processor Chipsets Supporting FSB Speeds of 667MHz and Hitachi's Virtualization Feature With Intel Virtualization Technology
Texas Instruments Announces First DLP .55 XGA Chip
Maxim Provides Revenue And EPS Guidance For Q3 Of Fiscal 2005
TI's Julie England Outlines Strategy to Drive Far-Reaching Applications for Wireless RFID Technology
Texas Instruments Delivers EPC Gen 2 Tag Emulators to RFID Reader and Printer Manufacturers to Ensure Interoperability
Ember and Atmel Bring Ultra-low Power 2.4 GHz ZigBee Networking and Microcontroller Platform to Market
Toshiba Launches White LED Driver IC Targeted at Cell Phone Backlighting Applications
Appro Brings 64-bit Intel Xeon Processors, InfiniBand and PCI Express Technologies to XtremeBlade Solution
Silicon Image Enables PC/CE Convergence With Industry's First HDMI Transmitters for PC Platforms
Zarlink Targets Growing Voice-over-Packet Gateway Market with New H.110 TDM Switch
Altera's Stratix II Family Leads the Industry With 2X Signal Integrity Performance Over Competing FPGAs
Silicon Image HDMI and Serial ATA Core IP Available in State-of-the-Art Process Technologies
Lattice Semiconductor Launches Low-Cost, Non-Volatile FPGAs
National Semiconductor Technology Revolutionizes Temperature Sensing for Sub-Micron CPUs, ASICs and FPGAs
Marvell(R) Exhibits Industry's First Networking Server I/O Module (SIOM) at Intel Developer Forum
AMCC Builds Upon High-Speed CMOS Design and Electronic Dispersion Compensation Expertise with 10Gbps Dual Clock Data Recovery Device for XFP Module Market
Ziptronix Appoints Phil Nyborg As New CEO; Semiconductor Industry Veteran Tapped to Commercialize Proprietary Technology for Three-Dimensional Integrated Circuits
More EDA in the News and More IP & SoC News
Upcoming Events...
--Contributing Editors can be reached by clicking here.
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