Re: processor speed vs 32-bit

On Wed, 2005-11-09 at 12:06, Jeffrey Beckstrom wrote:
> Given that the Itanium2 processor speed is less than what you can get
> with 32-bit processors, how does performance compare.

I assume you mean "clock speed" when you say "processor speed".  Clock
speed is a poor indicator of processor performance.  Processor
performance is better expressed as
  performance = cycles/sec * work/cycle = work/sec
The cycles/sec is the clock speed.  The work/cycle is how much work the
processor can do in a single cycle.  A pentium4 has a higher clock speed
than an Itanium2, but Itanium2 does much more work per cycle than
Pentium4 does.  The result is that they have similar performance for
some benchmarks, despite the fact that pentium4 has higher clock speeds.

The same issue can be seen among 32-bit processors.  For instance, a
1.13GHz Pentium3 is roughly the same speed as a 1.3GHz Pentium4.  This
is because a Pentium3 does more work per cycle than a Pentium4.  A
Pentium4 has more performance than Pentium3 only because they scale to
higher clock frequencies, thus overcoming the reduced work/cycle figure.

Performance varies greatly from one processor to the next, depending on
workload.  You can find performance figures for one popular set of
benchmarks at
  http://www.spec.org