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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 |
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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
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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
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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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