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Suggestions for Core 2 Duo systems that use PCI - not PCI express?



 
 
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  #1  
Old April 15th 09, 12:55 PM posted to alt.comp.hardware,alt.comp.hardware.pc-homebuilt
Geoff
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Posts: 692
Default Suggestions for Core 2 Duo systems that use PCI - not PCI express?

Hello,

I actually do not see why a newer core would be faster. 45 nm technology,
for example, is the size of the gate or transistor, and more can be placed
on the chip but that, by itself, would not mean faster.

The only two thing I can think of, with regard to the core only, not the
caches, etc. is the fact that they have instructions for moving data 64 bits
at a time and a higher clock speed.

The clock speed limit has been reached and most/many programs are 32 bit,
so, they would not be doing 64-bit register moves.

The only other thing is possibly there are scenarios they can optimize for,
at the cpu level, but that would not make a cpu 4 or 5 times faster.

IMHO.

--g


  #2  
Old April 15th 09, 07:00 PM posted to alt.comp.hardware,alt.comp.hardware.pc-homebuilt
Rarius
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Posts: 149
Default Suggestions for Core 2 Duo systems that use PCI - not PCI express?


"geoff" wrote in message
...
Hello,

I actually do not see why a newer core would be faster. 45 nm technology,
for example, is the size of the gate or transistor, and more can be placed
on the chip but that, by itself, would not mean faster.


45nm architecture offers more than just more transistors per sq mm.

Firstly the transistors are closer together and the chip is smaller... this
means that the time taken to get signals around the chip is reduced.

Secondly, the architectural techniques improve with each new generation.
This particularly effects things like the efficiency of the cache. Each C2D
core is generally 20-30% faster than a P4 core at the same clock speed.

The only other thing is possibly there are scenarios they can optimize
for, at the cpu level, but that would not make a cpu 4 or 5 times faster.


I agree that 4-5 times as fast is a little excessive. An improvement of
2.5x-3x is more like it. Remember that a C2D has at least 2 cores, the P2
only has one. Given that each core is faster and an improvement in RAM
speed, you have a 3 times improvement over a P4. A C2Q chip with 4 cores
could easily manage 4-5 times the performance of a P4.

Remember that there is ALWAYS more than just one thing going on in a modern
computer. Even if the main application is singlethreaded, the OS, device
drivers, other programs running in the background will use the other cores,
leaving the first core to run 100% on the main app. This in itself will
often result in a 20-30% performance increase. On the other hand, many apps
are limited by things other than the CPU, such as RAM and HDD.

Rarius



  #3  
Old April 15th 09, 08:00 PM posted to alt.comp.hardware,alt.comp.hardware.pc-homebuilt
DevilsPGD[_3_]
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Posts: 181
Default Suggestions for Core 2 Duo systems that use PCI - not PCI express?

In message "geoff"
was claimed to have wrote:

I actually do not see why a newer core would be faster. 45 nm technology,
for example, is the size of the gate or transistor, and more can be placed
on the chip but that, by itself, would not mean faster.

The only two thing I can think of, with regard to the core only, not the
caches, etc. is the fact that they have instructions for moving data 64 bits
at a time and a higher clock speed.

The clock speed limit has been reached and most/many programs are 32 bit,
so, they would not be doing 64-bit register moves.

The only other thing is possibly there are scenarios they can optimize for,
at the cpu level, but that would not make a cpu 4 or 5 times faster.


There are a ton of other changes that can be made to improve efficiency.

The change from a 386 to 486 was one of the most staggering, at equal
clock speeds the 486 was twice as fast for many instructions.

The picture is far more complex with modern CPUs, but many operations a
CPU can perform entirely on chip still take more then one clock cycle to
complete, anything that hits the various caches or system RAM will take
many more cycles, this leaves room for substantial improvement.

Some CPUs use predictive branching to move forward while waiting for
data to return, essentially making a guess, if they guessed right on the
results of the slow operation, the delay from the slow operation is
negated. If they guessed wrong, no harm done aside from a bit of energy
consumed.

Compare the performance of a Core 2 core vs an Atom core, for example.
Atom cores perform slower at equal clock speeds vs a Core 2 CPU, but
also have a more favourable watterformance ratio, so they're ideal for
installations where power savings is more important then performance.
One of the big things Atom processors don't do is predictive processing,
instead they offer Hyperthreading, which at least potentially allows a
single core to work on something else while waiting on a slow operation,
but if there is no other real work done, no power is wasted on incorrect
branches.

There is a lot more at play here then raw clock speed, especially when
comparing CPUs optimized for different purposes, the P4 -- Core/Core 2
architecture signaled a shift from raw MHz rates to looking at overall
performance, and to some extent performance-per-watt.
  #4  
Old April 16th 09, 02:15 AM posted to alt.comp.hardware,alt.comp.hardware.pc-homebuilt
Paul
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Posts: 13,364
Default Suggestions for Core 2 Duo systems that use PCI - not PCI express?

geoff wrote:
Hello,

I actually do not see why a newer core would be faster. 45 nm technology,
for example, is the size of the gate or transistor, and more can be placed
on the chip but that, by itself, would not mean faster.

The only two thing I can think of, with regard to the core only, not the
caches, etc. is the fact that they have instructions for moving data 64 bits
at a time and a higher clock speed.

The clock speed limit has been reached and most/many programs are 32 bit,
so, they would not be doing 64-bit register moves.

The only other thing is possibly there are scenarios they can optimize for,
at the cpu level, but that would not make a cpu 4 or 5 times faster.

IMHO.

--g


It is the clock speed times the number of instructions processed
in parallel, that gives the total number of instructions processed.

The Core2 has slightly better parallelism, and also has
an instruction fusion feature, where two instructions
can be bundled together. It means on average, it handles
more instructions per clock cycle, than the previous
processors.

What I've tried to do, in this thread, is offer you benchmarks
run by other people. Could some of the results be faked ?
I suppose so. SuperPI was modified slightly, to try to prevent
faking the results. There is a validator, for example, which
is intended to make cheating difficult.

http://www.xtremesystems.com/pi/

At the very least, you can download SuperPI, and replicate
the 2GHz Mobile Pentium 4 - M result, and see if it agrees.

http://www.xtremesystems.com/pi/super_pi_mod-1.5.zip

Paul
 




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