On 1/20/2012 2:23 PM, Rob Seaman wrote, in part:
There is plenty of prior art to consult here on both the CS side (early Crays already minimized cable runs to mitigate light speed constraints, it is commonplace today) and on the physics side (e.g., Planck units*). Workflow logistics and systems engineering are still needed to figure out the appropriate trade-offs for whatever purpose.There is unlikely to be one timekeeping methodology appropriate for all purposes, for instance this amazing video: http://web.mit.edu/newsoffice/2011/trillion-fps-camera-1213.html Rob -- * The Planck length is 25 orders of magnitude smaller than twice the Bohr radius (i.e., the diameter of a hydrogen atom). The Planck time is 5.391 x 10^-44 s, FWIW.
The time scale which a computer must keep track of while operating is different than the time scale which must be considered while designing the computer. The former is more likely to be time-of-day or time-since-an-epoch while the latter is more likely to be duration. I have been involved in the design of computers with a 500 ps clock period but design calculations were carried out with a resolution of about 1 ps.
A gross example of being aware of the location of various parts of a computer system would be an auction web site where bids are considered received when they arrive at any of the web site's servers. One solution would be to time-stamp the bids at the first server they arrive at; an alternate approach would be to subtract the transmission delay from the first-received server to the server that decides who won. It's difficult to predict what applications might require awareness of much
shorter transmission delays. Gerard Ashton _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
