From: Bill Stewart <stewarts@ix.netcom.com>
Date: Thu, 24 Jul 1997 04:57:49 +0800
To: cypherpunks@toad.com
Subject: Re: geodesic -- FPGAs
In-Reply-To: <m0wqGB6-000043C@r38h28.res.gatech.edu>
Message-ID: <3.0.2.32.19970723134153.006f0890@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



Tim replied:
>Why not replace your entire architecture with reconfigurable hardware?
>Because factors of 2 or 3 or 4 or more are still important to people.
>Witness the clamor to upgrade from 166 MHz Pentia to 200 MHz MMX Pentia,etc.
>Now tell those folks that the FPGA version will cost several times as much
>and have the performance of a 90 MHz 486. Or less.
>All for what? So they can issue a "reconfigure yourself" command and have
>their machine spend a few minutes reprogramming itself into, what, a Mac?

A machine running on a reconfigurable FPGA will need an operating system
that's not from Microsoft, so you get a factor of 4 or more back :-)
But realistically, while FPGAs may be good for running special applications,
you won't use it for random applications on different web pages;
general-purpose processors get better and better at that.
It might make an interesting peripheral, though, as DSPs once did.
LISP machines were nice, but it was much easier to stay on the
price-performance curve by tuning software better for general-purpose
machines than by using elegant software on customized hardware;
a 2:1 or 4:1 speed advantage is gone in 1-3 years, or faster if
somebody improves the compiler, and there are lots more people
improving compilers for mainstream machines than custom machines.

Over the years there have been reconfigurable machines.
VAXes used to have Writeable Control Store microcode;
other than an occasional bux fix or update to the machine,
the only people who used it were either very scary, very foolish,
or had too much time on their hands, or else they were trying to do
things that were way beyond the capabilities of the fine 1 MIPS machine
they needed.  (I used to play with virtual memory tunings,
since it's hard to get a simulation algorithm that really needs
14MB of RAM to work well in a huge 4MB machine, and the normal
virtual memory tunings got thrashed to death.  WCS is worse...)




#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk/pub/crypto/pgp
#   (If this is a mailing list or news, please Cc: me on replies.  Thanks.)