Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!oliveb!amdahl!tetons!bb
From: bb@tetons.UUCP (Bob Blau)
Newsgroups: comp.arch
Subject: quest for breakthroughs (long)
Keywords: architecture, breakthrough, technology
Message-ID: <740@tetons.UUCP>
Date: 10 Feb 89 20:52:42 GMT
Organization: Amdahl Corp., Rexburg, ID
Lines: 70


  This news group is stuck in an endian rut and strung out on history.
How about an exercise in creativity?  The goal is to use computer
architecture as the basis for directing future technological advances.
 
  Imagine that you are the enlightened head of Imaginary Computer Corp's
architecture department.  Your job is to tell us (the enlightened
scientists at the research lab) exactly what sort of technological
breakthrough would help you the most.

  What are your assumptions?
End Product: Embedded controller, PC, Workstation, Mini, SuperMini,
             MiniSuper, Mainframe, Super, ... 
Architecture:RISC, CISC, Vector, Massively parallel, VLIW, Shared memory
             multiprocessor, ...
Application: Home, Business, Engineering, Scientific, Manufacturing, ...
Timeframe:   Next year, in 5 years, in 10 years, ...

  What problems are you trying to solve?
- Performance, Cost, Complexity, Size, Reliability, ...

  Breakthrough examples:
- Practical X-Ray lithography creating 1 million gate CMOS chips
- Quantum transistors and high temperature superconductor "metallization"
  layers creating femtosecond propagation delays
- Fiberoptic advances creating 1 Gigabyte/sec cable or bus bandwidths
- Optical disc advances creating terabyte 3.5" optical discs
- Nanotechnology inventions creating microscopic computers
- ...

  Keep in mind system constraints like memory and IO bandwidth, power
and cooling, packaging limitations, reasonable economic assumptions, 
and balanced system design.  For instance an engineering workstation
manufacturer may dream of femtosecond gates in 10 years, but the
development and manufacturing costs would probably make the technology
prohibitively expensive for a workstation in that timeframe.  The memory
and IO to support that kind of cycle time also would not fit with
workstation cost, size, and software.
  
  Try not to expect too many breakthroughs at once, magically
eliminating bothersome constraints, but also making the scenario
implausible.  For instance, femtosecond propagation delay gates are
highly unlikely in commercial products in the next 10 years. First, 
they will require breakthroughs in the commercialization of quantum
transistors. Second, in order to derive real benefit from them,
breakthroughs in reducing on-chip and off-chip wire delays will also
be necessary.  The combination of two breakthroughs at the same time
strains credibility (but isn't impossible.)

  At what point do technology changes affect the architecture? At what
point do you get diminishing returns?

  Chip density: 50K gates -> 100K -> 500K -> 1M -> 5M -> ?
  Chip pinout: 250 pins -> 400 -> 800 -> 1000 -> 2000 -> ?
  Propagation delays: 500ps -> 100ps -> 20ps -> 5ps -> 500fs -> ?
  Chip power dissipation: 1 Watt/chip -> 10 -> 20 -> 50 -> 100 -> ?
  Cable bandwidth: 100 Mbits/sec -> 500M -> 1G -> 10G -> 100G -> ?
  ...

  The intent of this exercise is to discuss what kind of technology advances
really benefit a particular computer architecture. You may want to attack
the problem from the other side, starting with a breakthrough and
determining which architecture would be most suitable.


Apply: Standard disclaimers
-- 
  Bob Blau       Amdahl Corporation    143 N. 2 E., Rexburg, Idaho 83440
  UUCP:{ames,decwrl,sun,uunet}!amdahl!tetons!bb           (208) 356-8915
  INTERNET: bb@tetons.idaho.amdahl.com