Re: (no subject)

["Brian J. Bernstein" <bernstbj@ix.netcom.com>]

pubpc1@library.ucla.edu wrote:
> 
> Did you all know that the CPU in the Mars Pathfinder Sojourner
> Rover is an 8-bit Intel 80C85 running at 4MHz?  It was picked
> for its low power consumption.  I'd think that an equally low
> power, but more powerful, 16-bit WDC 65C816 running at 20MHz
> would do more and do it faster.

  Do you know the power consumption specs of the 80C85 vs the 65C816? 
  
  First, an 8 bit processor (properly designed) will use less power than
a 16 bit processor. Granted it is a rather insignificant difference, but
in the long run (and on Mars) it could mean the difference between
getting that last photo back to earth. Less data lines = less lines to
'charge'

  Second, a 4MHz processor will use less power than a 20MHz processor.
Not technically the same, but in principle it is: a motor spinning at 4
(say.. thousand) cycles per second needs less energy than one spinning
at 20 thousand cycles per second.

  Third, the rover isn't computing anything amazing, it's simply moving
with the aid of sensors and the direction of a program sent to it a day
beforehand. You don't need a number cruncher for this kind of duty. 4MHz
is still pretty damn fast, its just the software of today with GUIs and
hardware abstraction and (blah blah blah) requires 400 MIPS to work
decently.

  Fourth, the government loves Intel and probably doesn't care much
about WDC

  Fifth, who outside of the IIgs and C64 world really cares about the
65816 anyway? ;)

-- 
Brian J. Bernstein
bernstbj@ix.netcom.com
http://www.netcom.com/~bernstbj/