Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!apple!well!nagle
From: nagle@well.UUCP (John Nagle)
Newsgroups: comp.ai
Subject: Building a brain, revisited
Keywords: brain computer MIPS
Message-ID: <15439@well.UUCP>
Date: 9 Jan 90 20:47:32 GMT
Distribution: comp
Lines: 56



     We have the semiconductor technology to build a brain.

     Assume one accepts Hans Moravec's calculation that a human
equivalent robot is 10^14 bits per second.  (See "Mind Children",
pages 64-65).  Assume that a floating point operation produces 64 bits
of new information per operation.

     Last week, Motorola announced a new "SuperChip".  As yet unnamed,
this part, developed for the DoD Very High Speed Integrated Circuit
program, contains over 4 million transistors and delivers 200
megaflops, or 200 million floating point operations per second.  It's
a single-chip computer, but, of course, requires external memory and
some external support.

     A human brain equivalent would thus require about 8,000 such
parts, plus memory and supporting parts.

     For packaging, let's assume a layout similar to that used in the
Ncube Inc.  Hypercube.  Ncube puts 64 processors with their memory on
a board about 30" square, and puts 16 boards in a blue cube one meter
on a side, for 1024 processors per cabinet.  Ncube's single chip
processor is only a 1 MIPS machine comparable to a VAX 11/780, so
we're talking about a 200:1 performance improvement over the
1986-vintage Ncube machine.  In the Ncube, each processor had 128KB of
local memory, implemented with 256K RAMs.  Today, we would probably
want a 4Mbyte SIMM per CPU, which would occupy about the same amount
of real estate.

      Assuming one 4Mbyte SIMM per processor and one custom support
chip per CPU to handle memory control, fault tolerance control (a
feature of this new part), and interprocessor communication, each
board would contain 64 processors and 0.25 gigabyte of RAM.  Each
cabinet, only one meter on a side, would contain 1024 processors and
about 250 gigabytes of RAM.

      A brain-sized system would thus consist of eight such cabinets,
for a total of 8192 processors and 2 terabytes of RAM, with a
computing power of 1.6 teraflops.  It would occupy about a space about
four feet deep, four feet high, and 25 feet long.

      Cost can only be roughly estimated at this point.  But assume
that the CPU chip costs $1000 in quantity, the support chip $500, and
the 4MB of RAM $500.  Then the pure parts cost per CPU is $2000.
Assume that the entire system costs twice its parts cost.  This gives
us a price of $32,000,000.  This is in the price range of the largest
supercomputers today.  Of course, the price can be expected to decline
over time, probably at the historical rate of an order of magnitude
every three or four years.

      Agreed that we have no idea how to program such a piece of
machinery to be intelligent.  But it could be built today.


                                        John Nagle