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Increasing RAM decreases CPU time!!!

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Old   April 1, 2004, 13:57
Default Increasing RAM decreases CPU time!!!
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Hi everybody,

I had an interesting experience about the "RAM problem" in FLUENT. I ran the same job with two different computers. First: P4 2.8 Ghz with 2GB Ram, second: P4 3.0 Ghz with 1GB Ram. My job was using exactly the same RAM capacity (500 KB) for each computer. But, when I compared the CPU time for each, I saw that the performance of the second computer (although it has a faster CPU than first) was about 40 per cent less than the first one. Then, I concluded that increasing RAM in a computer must decrease the CPU time. So can it be right: More physical free memory you get in your computer, in much shorter times the jobs can be converged? What do you think?

PS: Operation systems were the same for the computers.

Best Regards...
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Old   April 2, 2004, 14:57
Default Re: Increasing RAM decreases CPU time!!!
Allan Walsh
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I think that RAM is not RAM. That is, there are many different types of RAM, operating at different speeds. Any idea what you have in your different systems?

Or perhaps it is not that simple and % of CPU usage was not the same for both cases - say if other background applications grab some clock cycles.
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Old   April 5, 2004, 06:21
Default Re: Increasing RAM decreases CPU time!!!
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Did you check hyperthreading on second computer?
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