Howard L. Davidson

Optical interconnects: out of the box forever?

Based on a variety of optimization criteria, recent research has suggested that optical interconnects are a viable alternative to electrical interconnects for board-to-board, chip-to-chip, and on-chip applications. However, the design of modern high-performance computing systems must account for a variety of performance scaling factors that are not included in these analyses. We will give an overview of the performance scaling that has driven current computer design, with a focus on architectural design and the effects of these designs on interconnect implementation. We then discuss the potential of optics at each of these interconnect levels, in the context of extant electrical technology.

Optical interconnections within modern high-performance computing systems

Optical technologies are ubiquitous in telecommunications networks and systems, providing multiple wavelength channels of transport at 2.5-10 Gbps data rates over single fiber-optic cables. Market pressures continue to drive the number of wavelength channels per fiber and the data rate per channel. This trend will continue for many years to come as e-commerce grows and enterprises demand higher and reliable bandwidth over long distances. E-commerce, in turn, is driving the growth curves for single-processor and multiprocessor performance in data-base transaction and Web-based servers. Ironically, the insatiable taste for enterprise network bandwidth, which has driven up the volume and pushed down the price of optical components for telecommunications, is simultaneously stressing computer system bandwith-increasing the need for new interconnection schemes-and providing for the first time commercial opportunities for optical components in computer systems. This paper will center primarily on the use of optical interconnects within commercial digital computing systems, particularly workstations and servers, and will address mainly board-board interconnects within a single cabinet or box. We feel this is the most likely utilization of optics in commercial computer systems for the next decade. We will also provide a practical analysis of inter-and intrachip optical interconnects and the difficulties they face in real systems.

The chip-multithreading architecture and parallel optical interconnects

Tens of terabits-per-second bandwidth will be required for revolutionary chip-multithreading (CMT) architectures. In this presentation, we will review the technical challenges for electrical signaling and discuss how parallel optical interconnects could be valuable in CMT architectures.

Can optical interconnects be sufficiently parallel to support the needs of computer systems

The level of parallelism required for computer interconnects represents significant opportunities and serious challenges for optical interconnects. In this presentation, we will discuss several challenges and present some potential optical interconnect solutions.