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Old   February 6, 2010, 07:34
Default i7-720QM vs i5-520M
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Nicolas Gomez Osorio
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Hello all

Im going to buy a new laptop, an eventhough I know laptops are not the best for CFD , i need one but im incertain in which to buy either a one that fits a i7 -720QM 1.66GHz or a i5-520M 2.4GHz. Im going to use FLUENT . I really apreciatte your advice
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Old   February 9, 2010, 05:13
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I think you better look at the power consumption and heat produced by the processor, and the cooling of the laptop. Whille running a laptop for a while at 100% CPU things can get pretty hot.
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Old   February 11, 2010, 02:15
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I have a laptop but it's head is heated so much but it worth me a lot.
Please give a better attention to this fact.
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Old   March 7, 2010, 13:52
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thank I will keep that on mind
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Old   September 29, 2010, 08:27
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Go for Dell M16 series. They are best for these purposes. You can visit dell site for further details on the specs.
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Old   February 14, 2011, 20:24
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I think for this subject cor i5 is better . I have laptop with 2.13 core i3 and take run with it well.
Plus CPU and Because of autosave in fluent RAM is very important .You must have CPU and RAM proportional .
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Old   February 15, 2011, 19:21
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I have an ASUS N61JQ laptop with an i7-720QM processor in it. It's very good for basic CFD computations when I'm at school and not able to use a more powerful computer. That said, I rarely use it on my lap, so heat hasn't been an issue for me. The cooling system has never let the CPU exceed 75C.

If you do a lot of parallel jobs go for the i7 for the fact that you can get 8 threads going. if you're not doing parallel processing, go for the i5 as it's serial processing speed is much faster.

As eman said, don't forget the RAM. I'd recommend upgrading whatever you get to 8GB at least.
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Old   February 15, 2011, 21:28
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Quote:
Originally Posted by aerospace_guy_ View Post
I have an ASUS N61JQ laptop with an i7-720QM processor in it. It's very good for basic CFD computations when I'm at school and not able to use a more powerful computer. That said, I rarely use it on my lap, so heat hasn't been an issue for me. The cooling system has never let the CPU exceed 75C.

If you do a lot of parallel jobs go for the i7 for the fact that you can get 8 threads going. if you're not doing parallel processing, go for the i5 as it's serial processing speed is much faster.

As eman said, don't forget the RAM. I'd recommend upgrading whatever you get to 8GB at least.
actually i belive that hypertreading slows down the computation. i do have a dell with i7 720 processors and 8gb of ram and in starccm is faster without hypertreading (or setting the affinity to a specific core, wich is the same). ht is supposed to be good for a lot of small programs wich use few power for a short time, not a huge number crunching beast like fluent or any other cfd sw.

my .02 cents
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Old   March 17, 2011, 00:18
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Hi Guys,

I am already using HP elitebook with Core i5. If the CFD program which you use has good multithreading capability it is really nice.

But things can become pretty hot running it at 100% performance continously...
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Old   March 29, 2011, 10:48
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Quote:
Originally Posted by sail View Post
actually i belive that hypertreading slows down the computation. i do have a dell with i7 720 processors and 8gb of ram and in starccm is faster without hypertreading (or setting the affinity to a specific core, wich is the same). ht is supposed to be good for a lot of small programs wich use few power for a short time, not a huge number crunching beast like fluent or any other cfd sw.

my .02 cents

On my laptop with an i7 running 8threads instead of 4 was significantly faster. I have not tried 4 threads without HT enabled so cannot compare that.
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Old   March 30, 2011, 02:21
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Quote:
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On my laptop with an i7 running 8threads instead of 4 was significantly faster. I have not tried 4 threads without HT enabled so cannot compare that.
mmm. this is intresting. could you please define the software used for the simulation, the operative system, the mesh size and the type of analysis you are running?

i do not exclude to be wrong, i'll do some comparisons in the future and it would be nice to have some form of data from other users.
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Old   March 30, 2011, 03:18
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It was a StarCCM, VOF calculation with 6DOF on a 3million mesh. This was running under windows 7 64 bit with 8GB RAM.

I also encountered the fact that disabling the HT in the past was significanlty faster, on other codes too. But when I asked someone I was told that if the code was designed with HT in mind that changes everything, but he was by no means an expert so that could be wrong.

I unfortunately do not have the time to run some benchmarks.
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Old   March 30, 2011, 03:43
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Quote:
Originally Posted by fastwave View Post
It was a StarCCM, VOF calculation with 6DOF on a 3million mesh. This was running under windows 7 64 bit with 8GB RAM.

I also encountered the fact that disabling the HT in the past was significanlty faster, on other codes too. But when I asked someone I was told that if the code was designed with HT in mind that changes everything, but he was by no means an expert so that could be wrong.

I unfortunately do not have the time to run some benchmarks.
i've got almost the same hw and sw setup (i use xp 64bit) and run analysis similar to your in both type and mesh size. when i'll have some time i'll do some benchmarks and post the results. unfortunately my licence is restricted to 4 cores, so i cannot evaluate the 8-cores using HT. any chance you can send me a .sim file of yours to compare the case i'm missing? or i could send you a case of mine, if you want to run it on 8 cores.
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Old   March 30, 2011, 17:35
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Certainly on a single processor it is unlikely for a CFD type load to be faster using HT with more threads as you will raise the amount of message passing involved.

If the OS is not smart enough to recognize real and virtual processors then it can schedule two processes onto one physical CPU and leave a real CPU unloaded. We ran into this problem with a Linux based OS. In this case using the same number of processes as HT cores would probably be faster as all cores are used all the time.

If you disable HT and run the same number of threads as cores then you are likely getting all the performance you can get out of a processor.
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Old   March 30, 2011, 21:42
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This is certainly interesting. I'm not using StarCCM, I am using Ansys CFX, but I must admit, I haven't tried using it with HT disabled. I shall have to run a few benchmarks sometime soon to see what the performance impact is when HT is off, instead of just setting affinity to physical cores.

As for the impact of the operating system, I've noticed once when running a four partition simulation in Win7 that CFX automatically populated the physical cores, (0,2,4 and 6) before it created a thread whose affinity was set to any of the logical cores. I've only noticed this once, so It may have something to do with the circumstances at the time. Could anyone else verify this? I'll pay closer attention next time I start a CFD simulation and see if I notice it again.
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Old   March 31, 2012, 00:57
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Quote:
Originally Posted by Megatron View Post
Hi Guys,

I am already using HP elitebook with Core i5. If the CFD program which you use has good multithreading capability it is really nice.

But things can become pretty hot running it at 100% performance continously...
Some peoples say i5 wont support Fluent , thats why i am hesitating to buy it, will windows 7 support fluent? what is your OS?
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Old   March 31, 2012, 07:59
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Why would i5 not support Fluent? Whoever told you that is pretty much an idiot. As far as operating systems go, there is a list of operating systems supported by ANSYS on their web pages but it also works on the non-officially-supported ones. On Windows 7 there are no problems with any of the ANSYS applications.
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