Keith Bierman's Weblog

Wednesday December 07, 2005

With All Due Respect Jonathan 9.6GHz is not the clock of our UltraSPARC T1 processor. As any hardware engineer knows, clock speed is a simply measurable entity, you stick  test leads on the appropriate wires and count the phase transitions. The correct number is 1.2GHz.

Now, as software engineers we know that folks like to compute theoretical maximum operation rates, and 1.2GHz * 8 cores does yield 9.6 GOPS as a theoretical limit. And thanks to many years of industry confusion, probably due to the infamous Dhrystone benchmark, clock rate and operations per second have become hopelessly confused in the minds of many. 

But fundamentally there is no link between clock and work done (you can have really, really simple instructions (the limiting case is a single instruction (but then you need a very large number of instructions per useful work done ;>)

As proved previously by our Opteron based systems should have demonstrated, clock speed isn't a solid predictor of performance (Intel has a faster clock, and poorer performance).

I suppose one can argue that it is "pleasing that in lots of scenarios we do see scaling that is in fact more or less linear with the core count". See a benchmark focused blog for examples.



(2005-12-07 14:52:04.0) Permalink Comments [1]