Erik de Castro Lopo wrote:
So, looking for wiggle room?
What do you mean by this ?
O Plameras wrote:
So, what is 'clock cycle' in your definition ?
My defintion like yours is irrelevant. However, a generally accepted
definition is here:
http://en.wikipedia.org/wiki/Clock_cycle
As it relates to (Intel)CPU see this:
http://www.google.com/search?hl=en&lr=&oi=defmore&defl=en&q=define:clock+cycle
As you can see, clock cycle is the time it takes to execute the simple
instruction set.
This definition is crucial if we want to
compare apples-with-apples. How does it relate to CPU speed ?
There is no direct relationship.
This is totally wrong. There is a direct relationship.
The relationship is that an Intel Pentium 4 with 1.5GHZ has a CPU that
can execute
1.5 billion intructions in one second if all of these instructions are
simple instructions.
Another way of saying this is that Pentium 4 - 1.5GHZ has 1.5 billion
clock cycles.
Some program codes need 1 clock cycles and others need more. With pipelining
1 clock cycle can handle more than 1 instructions.
But since not all instructions are simple, some instructions takes more
clock cycle
than others. A program will always have a mix of instructions from the
simple to
somewhat more complex.
And how do you measure CPU performance ?
I think performance benchmarks are the best measure of CPU
performance.
And remember, I was talking x86 CPU family and not AMD.
Have a look at this article:
http://techreport.com/reviews/2001q3/piii-1.2/index.x?pg=1
On the third page:
But the Pentium 4's deeply pipelined design can't deliver the
same performance, clock for clock, that the Athlon or Pentium
III can.
Ignore the Athlon for the moment, but notice how the review is
comparing Pentium 4 with Pentium III, both members of the x86
family.
Going back to your example in a previous post comparing Intel (2000MHZ)
and AMD(1400MHZ) CPU's is obviously wrong.
First, Intel and AMD do not have the same instruction sets.
Secondly, the simple Intel instruction is simpler than AMD's(i suspect),
meaning AMD's
simple instruction does more things that that Intel(I suspect) and their
architecture are
not similar as to have a meaningful comparison.
So, that is why you cannot compare Intel and AMD.
The whole point of my original post is that clock cycle is a basic
measure of
performance in that the shorter it is, the faster (execute more
instructions per unit
time) is the throughput (performance). Another way of saying this is in
a particular
Intel CPU family the bigger the MHZ the faster is the CPU.
So, to be a good programmer one has to understand these.
O Plameras
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