🚀 go-pugleaf

In article <RAULMILL.89Nov16083219@usc.edu> raulmill@usc.edu 
	(Raul Deluth Rockwell) writes:
>In article <TOMS.89Nov15114003@omews44.intel.com> toms@omews44.intel.com 
	(Tom Shott) writes:
>;> As we top 50 MHz for chip speed the biggest problem becomes getting data on
>;> and off chip. 
>;> One solution that has not been discussed is flip chip technology. In flip
>;> chip technology many die are mounted directly on a ceramic carrier.
>
>Another solution that I haven't seen much discussion of is using
>optical fibers with an ultra-high-speed serial protocol as a method
>for transporting data.

Today's nifty interconnect technologies (like flip chip) are great
because they reduce the interchip distance, the line capacitance, and
even the inductance. IBM's Thermal Conduction Module technology did
all of these.  The new packaging technology in the VAX 9000 should be
more-or-less competitive. (They use derated IC lithography to build
up a copper/plastic circuit board, and TAB-bond naked chips directly
to the board.)

The major difference between optical signals and electrical signals
is that optical signals don't interact: no crosstalk, the paths
aren't antennas, the signals can even interpenetrate. The problem
with using fibers is that they are made in a factory and can't be
formed on the spot.  Fibers would have to be placed and bonded in the
manner of wires. Tedious! The answer seems to be that we should form
optical channels directly onto a substrate, perhaps using a plastic.
There was a recent announcement of a material which can be made
nontransparent by exposure to (I think) UV. Advances like this
suggest that we might be able to make "circuit boards" that take
light directly from chip to chip. 

Next, we'd like to have integrated opto-electronic chips: that is,
optical emitters and detectors on the same chip with logic. This has
been a Holy Grail to the communications people, and they are about
there. However, it might be a lot easier to use the new lift-off
technologies. These allow one to build a chip, and then lift off the
top ten microns or so. The ideal would be to build optical devices,
lift them, and drop them onto logic chips.  There should be room, if
the chips only need bonding pads for power and ground.

-- 
Don		D.C.Lindsay 	Carnegie Mellon Computer Science