Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Method of Constructing a Central Processing Unit Using Light Communications

IP.com Disclosure Number: IPCOM000120334D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 102K

Publishing Venue

IBM

Related People

Chiu, C: AUTHOR [+2]

Abstract

A technique is described whereby a central processing unit (CPU) is fabricated by using opto-electronic integration light communications. The objective is: a) to increase the interconnect bandwidth of the CPU; b) to reduce the delta-i noise; and c) to increase CPU parallelism.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method of Constructing a Central Processing Unit Using Light Communications

      A technique is described whereby a central processing
unit (CPU) is fabricated by using opto-electronic integration light
communications.  The objective is:  a) to increase the interconnect
bandwidth of the CPU; b) to reduce the delta-i noise; and c) to
increase CPU parallelism.

      The utilization of opto-electronic integration for high-end
CPUs can provide significant advantages in that the small current
swing, approximately 1 MA, is sufficient for driving a laser diode.
In comparison, approximately 20 MA (1 volt logic swing into a 50-ohm
impedance) is necessary for the conventional electronic device.
Therefore, an optical interconnect can reduce the delta-i noise and
increase the CPU parallelism.  In addition, an optical input/output
(I/O) has increased bandwidth so that optical connectors can be
designed with far less signal dispersion. Also, system clock skew can
be reduced due to the fact that a sharper rise-time can be produced
with optical methods and that the higher bandwidth of optical
interconnects preserves the waveform.

      It is known that silicon is an excellent material for optical
detector applications (in the 0.5 to 0.9 micron region) and that
silicon dioxide can form the basis for film waveguides.  However,
silicon does not lase effectively.

      It has been demonstrated that GaAs can be expitaxally grown [*]
on silicon.  Fig. 1 shows the use of GaAs on a Si chip.  The chip
is C4 bounded to the Si substrate with a silicon dioxide waveguide.
The result is a simplified communication path in a CPU.  Signals are
propagated with light.  Laser diodes built with GaAs on Si are the
transmitter.  Waveguides and optical receivers are based on silicon
technology.

      Fig. 2 illustrates the waveguide portion.  The photodetector is
also made in terms of silicon.  Fig. 2a shows the use of phosphorus-
doped regions so as to have a higher index of refraction for guiding
the li...