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Calculations per second! Am I understand this right?

post #1 of 3
Thread Starter 
Modern CPUs on average run at about 3GHZ a second, I know that means 3 Billion calculations per second but what does a calculation consist of?? Is it a single calculation of for example 1+1=2 per clock cycle?

Also does this mean that a quad Core 3GHz CPU theoraticaly does 12 Billion calculations per second??
post #2 of 3
Quote:
Originally Posted by jcrew3002 View Post

Modern CPUs on average run at about 3GHZ a second, I know that means 3 Billion calculations per second but what does a calculation consist of?? Is it a single calculation of for example 1+1=2 per clock cycle?

Also does this mean that a quad Core 3GHz CPU theoraticaly does 12 Billion calculations per second??

One Hertz (Hz) is one cycle. It is related to but does not determine calculations, which are often measured in IPCs, or instructions per cycle. Assume a quad-core 3GHz CPU. If each core can perform 100 calculations per cycle, then you've got 300 billions calculations per second per core, or 1.2 trillion for the entire CPU. If they take 100 cycles to perform a single calculation, then they can only hit 30 million per core or 120 million overall. This assumes a perfect world with multi-threading, no latency, etc.
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post #3 of 3
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Quote:
Originally Posted by CynicalUnicorn View Post

One Hertz (Hz) is one cycle. It is related to but does not determine calculations, which are often measured in IPCs, or instructions per cycle. Assume a quad-core 3GHz CPU. If each core can perform 100 calculations per cycle, then you've got 300 billions calculations per second per core, or 1.2 trillion for the entire CPU. If they take 100 cycles to perform a single calculation, then they can only hit 30 million per core or 120 million overall. This assumes a perfect world with multi-threading, no latency, etc.

Ok good info thanks! So for example in Microsoft Word if from the pressing of the letter "A" till the time it is displayed on screen it takes only 5 cycles then at that instant the CPU is theoretically working at 20 Billion calculations per second per core per key pressed.

So the actual working speed of the CPU (time it takes to debug some program code from start to Finnish) is dependent on the program running through the CPU at 3GHz per second.

helps me to understand those CPU benchmarking programs thumb.gif
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