Should Core 2 Duo CPU not be theoretically slower than single core with double MHz?

Jason Stacy wrote:

When I run the same application on a two core system then it can occupy only ONE of the two cores
with 1.7 MHz. Because it is non-threaded it cannot request the other core as well.
So it must be slower (given all other side-conditions are equal).

Am I wrong?

Yes. You were wrong to cross-post to two groups while setting a
follow-up to only one of them.

But regarding your CPU question, "everything else equal" you are
correct. Why ask such an obvious question?

Just as obviously, if the CPU's are entirely different designs, or
have different amounts of cache, etc, then you no longer have that
simple "everything else equal" question.

Jason Stacy wrote:

When I run the same application on a two core system then it can occupy only ONE of the two cores
with 1.7 MHz. Because it is non-threaded it cannot request the other core as well.
So it must be slower (given all other side-conditions are equal).

Am I wrong?

Yes. You were wrong to cross-post to two groups while setting a
follow-up to only one of them.

But regarding your CPU question, "everything else equal" you are
correct. Why ask such an obvious question?

Just as obviously, if the CPU's are entirely different designs, or
have different amounts of cache, etc, then you no longer have that
simple "everything else equal" question.

On or about 21 May 2009 06:57:58 GMT did (Jason Stacy)
dribble thusly:

I wonder why a two-core CPU with lets say 2 * 1.7 Mhz is theoretically faster
than a single core with 3.4 MHz. I am NOT talking about additional features like
Pipeling and Hyperthreading but the core fact that the power is split over two cores.

If you're talking about a single core at 3.4GHz, then you're talking about a
Pentium 4, which is a horribly designed chip.

Considering just the speed of a single core, for comparison, that 3.4GHz P4 is
about the same speed as a 1.8GHz Core 2, or a 2.0GHz AMD Athlon X2. That's
how bad it is.

Performance varies from app to app, of course, so you'll no doubt be able to
find something single-threaded that runs faster on a 1.7GHz Core 2 than a
3.4GHz P4.

I guess the basic lesson you haven't learned is that pipelining and whatnot
matters. Not all CPU cycles are equal, which is why a modern 3000MHz chip is
quite a bit more than 30 times faster than an old 100MHz Pentium, and why a
100MHz Pentium completely outclassed a 100MHz 486.

On or about 21 May 2009 06:57:58 GMT did (Jason Stacy)
dribble thusly:

I wonder why a two-core CPU with lets say 2 * 1.7 Mhz is theoretically faster
than a single core with 3.4 MHz. I am NOT talking about additional features like
Pipeling and Hyperthreading but the core fact that the power is split over two cores.

If you're talking about a single core at 3.4GHz, then you're talking about a
Pentium 4, which is a horribly designed chip.

Considering just the speed of a single core, for comparison, that 3.4GHz P4 is
about the same speed as a 1.8GHz Core 2, or a 2.0GHz AMD Athlon X2. That's
how bad it is.

Performance varies from app to app, of course, so you'll no doubt be able to
find something single-threaded that runs faster on a 1.7GHz Core 2 than a
3.4GHz P4.

I guess the basic lesson you haven't learned is that pipelining and whatnot
matters. Not all CPU cycles are equal, which is why a modern 3000MHz chip is
quite a bit more than 30 times faster than an old 100MHz Pentium, and why a
100MHz Pentium completely outclassed a 100MHz 486.

If we previously had Pentium 3.8Ghz processors, then why can't they just
make 3.8Ghz dual or quad core processors? Why are they always at such low
speeds?

Is size really a factor? Can't they just make the chips an inch or two
larger to accomodate or will heat be the issue?

"Jason Stacy" wrote in message
...
I wonder why a two-core CPU with lets say 2 * 1.7 Mhz is theoretically
faster
than a single core with 3.4 MHz. I am NOT talking about additional
features like
Pipeling and Hyperthreading but the core fact that the power is split over
two cores.

Assume the following situation: A NON-THREADED application needs as much
CPU power as possible
for some computations. On a 3.4 Mhz machine it can occupied almost 99% of
the CPU power
(remaining 1 % are for system services).

When I run the same application on a two core system then it can occupy
only ONE of the two cores
with 1.7 MHz. Because it is non-threaded it cannot request the other core
as well.
So it must be slower (given all other side-conditions are equal).

Am I wrong?

J.

If we previously had Pentium 3.8Ghz processors, then why can't they just
make 3.8Ghz dual or quad core processors? Why are they always at such low
speeds?

Is size really a factor? Can't they just make the chips an inch or two
larger to accomodate or will heat be the issue?

"Jason Stacy" wrote in message
...
I wonder why a two-core CPU with lets say 2 * 1.7 Mhz is theoretically
faster
than a single core with 3.4 MHz. I am NOT talking about additional
features like
Pipeling and Hyperthreading but the core fact that the power is split over
two cores.

Assume the following situation: A NON-THREADED application needs as much
CPU power as possible
for some computations. On a 3.4 Mhz machine it can occupied almost 99% of
the CPU power
(remaining 1 % are for system services).

When I run the same application on a two core system then it can occupy
only ONE of the two cores
with 1.7 MHz. Because it is non-threaded it cannot request the other core
as well.
So it must be slower (given all other side-conditions are equal).

Am I wrong?

J.

shawn wrote:
If we previously had Pentium 3.8Ghz processors, then why can't they just
make 3.8Ghz dual or quad core processors? Why are they always at such low
speeds?

Is size really a factor? Can't they just make the chips an inch or two
larger to accomodate or will heat be the issue?


Heat is a BIG issue.
The Pentium IV (4) was the last to really push the speed barrier. Most
newer systems are now into multiple cores to achieve the improved speed.

There are many factors...

(a) The die area and manufactured size. Back in the day most were 90nm
or larger. Today 65nm and 45nm processes are available. Also, die area
is expensive and the larger the die the more of a chance for bad yields.

(b) The package or size you see on the outside is not always the same
size the CPU chip is on the inside. Another trick would be to
efficiently transfer the heat to the surface of the chip from the die.
In most CPUs I've seen that is what that little square in the middle is
doing for you. Then to efficiently transfer the heat from the square to
the heat sink. Making the square bigger may not be a really good
option; only so much and you may encounter breakage to the die
underneath and/or making a well where the heat gets concentrated instead
of dissipated.

(c) It would probably be more than an inch or two to get the needed
cooling. The ridiculous power usage is incredible on many of these new
systems. I use to be able to run a FULL TOWER on a 200-watt or 250-watt
power supply. Some systems today supply 900-watt or more!!! In my
opinion that is a lot of power for a PC.

James

shawn wrote:
If we previously had Pentium 3.8Ghz processors, then why can't they just
make 3.8Ghz dual or quad core processors? Why are they always at such low
speeds?

Is size really a factor? Can't they just make the chips an inch or two
larger to accomodate or will heat be the issue?


Heat is a BIG issue.
The Pentium IV (4) was the last to really push the speed barrier. Most
newer systems are now into multiple cores to achieve the improved speed.

There are many factors...

(a) The die area and manufactured size. Back in the day most were 90nm
or larger. Today 65nm and 45nm processes are available. Also, die area
is expensive and the larger the die the more of a chance for bad yields.

(b) The package or size you see on the outside is not always the same
size the CPU chip is on the inside. Another trick would be to
efficiently transfer the heat to the surface of the chip from the die.
In most CPUs I've seen that is what that little square in the middle is
doing for you. Then to efficiently transfer the heat from the square to
the heat sink. Making the square bigger may not be a really good
option; only so much and you may encounter breakage to the die
underneath and/or making a well where the heat gets concentrated instead
of dissipated.

(c) It would probably be more than an inch or two to get the needed
cooling. The ridiculous power usage is incredible on many of these new
systems. I use to be able to run a FULL TOWER on a 200-watt or 250-watt
power supply. Some systems today supply 900-watt or more!!! In my
opinion that is a lot of power for a PC.

James

shawn wrote:
If we previously had Pentium 3.8Ghz processors, then why can't they just
make 3.8Ghz dual or quad core processors? Why are they always at such low
speeds?

Is size really a factor? Can't they just make the chips an inch or two
larger to accomodate or will heat be the issue?

This is a question best asked in a computer architecture group, as there
are multiple factors at work.

*******

Much has changed over the years. The Prescott generation was the last
generation with what appeared to be a serious leakage problem. 25% of
the power used, was just wasted, and did no useful work. This could
not continue. The switch to 65 or 45 or 32nm could not fix the leakage
issue, which would only get worse. With each generation, the transistors
had to be redesigned, the material science changed, to make the
scaling of the transistor worthwhile. If a Prescott transistor was
just made smaller, there'd be a smoking hole in the ground.

As I understand it, more complicated structures are used now for the
gates. Some transistor structures have stuff added, to reduce or eliminate
leakage. When absolute speed is needed, perhaps a small percentage of the
structures still leak, in the interest of getting the most speed. So they
pick and choose, in the interest of reducing the leakage of the processor
to manageable levels. I think they've done an admirable job, based on
my own power measurements (my 65W processor uses 36W max, on a 65nm
Core2 Duo).

The pipeline length on the new processors is shorter. They really
couldn't continue on the "Prescott" path, because AMD was kicking
their ass. The result is

lower frequency
shorter pipeline
able to retire more instructions per clock cycle (parallelism inside a core)
multiple cores (only really impressive, for software that uses it well)

The thing is, technology exists to do really silly things, but for the
retail price point, you'd be saying "no thanks, I'd rather buy a car".
The current delivered technology is cheap and powerful, so stop complaining :-)

Technology exists that can run at 40GHz. You could build a processor with it
(if say, you had a bar bet with a buddy). No memory subsystem could reasonably
supply it with information. But it would make a great room heater.

(In the following article, some of the references to frequency, are for
Ft of the transistor. It takes multiple transistors to make a flip-flop
storage element. And the operating frequency of one of those, will be
lower than the numbers seen in this article. This is just to show that
there is stuff other than CMOS available to build circuits. The fiber
optics criss-crossing the nation, rely on some of the following
technology, to work at incredible speeds.)

http://en.wikipedia.org/wiki/Heteroj...lar_Transistor

http://www.ntt.co.jp/news/news06e/0609/060929a.html

"InP ICs, which can be operated at over 50 GHz were used in
multiplex and demultiplex circuits..."

HTH,
Paul


"Jason Stacy" wrote in message
...
I wonder why a two-core CPU with lets say 2 * 1.7 Mhz is theoretically
faster
than a single core with 3.4 MHz. I am NOT talking about additional
features like
Pipeling and Hyperthreading but the core fact that the power is split over
two cores.

Assume the following situation: A NON-THREADED application needs as much
CPU power as possible
for some computations. On a 3.4 Mhz machine it can occupied almost 99% of
the CPU power
(remaining 1 % are for system services).

When I run the same application on a two core system then it can occupy
only ONE of the two cores
with 1.7 MHz. Because it is non-threaded it cannot request the other core
as well.
So it must be slower (given all other side-conditions are equal).

Am I wrong?

J.

shawn wrote:
If we previously had Pentium 3.8Ghz processors, then why can't they just
make 3.8Ghz dual or quad core processors? Why are they always at such low
speeds?

Is size really a factor? Can't they just make the chips an inch or two
larger to accomodate or will heat be the issue?

This is a question best asked in a computer architecture group, as there
are multiple factors at work.

*******

Much has changed over the years. The Prescott generation was the last
generation with what appeared to be a serious leakage problem. 25% of
the power used, was just wasted, and did no useful work. This could
not continue. The switch to 65 or 45 or 32nm could not fix the leakage
issue, which would only get worse. With each generation, the transistors
had to be redesigned, the material science changed, to make the
scaling of the transistor worthwhile. If a Prescott transistor was
just made smaller, there'd be a smoking hole in the ground.

As I understand it, more complicated structures are used now for the
gates. Some transistor structures have stuff added, to reduce or eliminate
leakage. When absolute speed is needed, perhaps a small percentage of the
structures still leak, in the interest of getting the most speed. So they
pick and choose, in the interest of reducing the leakage of the processor
to manageable levels. I think they've done an admirable job, based on
my own power measurements (my 65W processor uses 36W max, on a 65nm
Core2 Duo).

The pipeline length on the new processors is shorter. They really
couldn't continue on the "Prescott" path, because AMD was kicking
their ass. The result is

lower frequency
shorter pipeline
able to retire more instructions per clock cycle (parallelism inside a core)
multiple cores (only really impressive, for software that uses it well)

The thing is, technology exists to do really silly things, but for the
retail price point, you'd be saying "no thanks, I'd rather buy a car".
The current delivered technology is cheap and powerful, so stop complaining :-)

Technology exists that can run at 40GHz. You could build a processor with it
(if say, you had a bar bet with a buddy). No memory subsystem could reasonably
supply it with information. But it would make a great room heater.

(In the following article, some of the references to frequency, are for
Ft of the transistor. It takes multiple transistors to make a flip-flop
storage element. And the operating frequency of one of those, will be
lower than the numbers seen in this article. This is just to show that
there is stuff other than CMOS available to build circuits. The fiber
optics criss-crossing the nation, rely on some of the following
technology, to work at incredible speeds.)

http://en.wikipedia.org/wiki/Heteroj...lar_Transistor

http://www.ntt.co.jp/news/news06e/0609/060929a.html

"InP ICs, which can be operated at over 50 GHz were used in
multiplex and demultiplex circuits..."

HTH,
Paul


"Jason Stacy" wrote in message
...
I wonder why a two-core CPU with lets say 2 * 1.7 Mhz is theoretically
faster
than a single core with 3.4 MHz. I am NOT talking about additional
features like
Pipeling and Hyperthreading but the core fact that the power is split over
two cores.

Assume the following situation: A NON-THREADED application needs as much
CPU power as possible
for some computations. On a 3.4 Mhz machine it can occupied almost 99% of
the CPU power
(remaining 1 % are for system services).

When I run the same application on a two core system then it can occupy
only ONE of the two cores
with 1.7 MHz. Because it is non-threaded it cannot request the other core
as well.
So it must be slower (given all other side-conditions are equal).

Am I wrong?

J.