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Old   February 10, 2017, 23:49
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Dear all,
I want to upgrade my desktop PC for CFD calculation. I don't use this for extreme computation which requires lots of RAM. I solve models requiring 2-16 GB of RAM (usually just 4 GB of RAM).

My current PC spec is as follows (via CPU-z):
CPU : i3-2100 @ 3.1 GHz (2 cores, 4 thread) - 3 MB cache
Mobo : Asus P8H61-M LX
Memory : total 12 GB, DRAM Freq: 665.1 MHz, CAS Latency (CL) = 11
(1) Slot #1 : 8 GB - DDR3 Corsair PC3-12800K (800 MHz)
(2) Slot #2 : 4 GB - DDR3 PC3-10700 (667 MHz)

If I want to upgrade, will it worth if i upgrade it into i5/i7 quad-core processor (Sandy bridge/Ivy bridge)? Should I replace the slot #2 RAM into 8 GB to enable dual-channel?

Any suggestions will be appreciated. Thank you.
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Old   February 11, 2017, 03:58
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So you want to keep that motherboard and invest as little money as possible?
Then buy a used I5-2500 and additional 8GB of RAM. An I7 processor is not worth your money since it only adds SMT, a feature that is rarely beneficial for CFD workloads.
By the way, your system should already use dual-channel to some extent, it is called asymmetric dual channel. However, part of the memory still operates in single-channel mode so upgrading to 2x8GB is a god idea anyway.
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Old   February 11, 2017, 06:09
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Thanks Alex!
Yes, I want to keep this motherboard, since if I want to change, it'll need almost complete new build. I want to build new pc in the future. But for now, just upgrade and spend as little money as possible. 😀
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Old   February 12, 2017, 06:49
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Dear all,
I want to ask, does memory bandwidth effect CFD calculation speed significantly? If yes, I'll consider replacing mobo, CPU, and memory and replace them with faster DDR3/DDR4 RAM.

Thanks
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Old   February 12, 2017, 08:03
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With enough raw processing power from the CPU, memory bandwidth becomes the single most important bottleneck for CFD simulations.
If there is a significantly better option for you depends on how much money you want to spend.
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Old   February 15, 2017, 11:57
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Thanks for the reply, Alex!
I have upgraded to i5-2500 (bought used one). It decreases calculation time up to 40%-50% from my previous i3-2100.

If i run the CFD software like Fluent/CFX, the temperature usually increases to 80 deg C, with full load with Intel stock CPU. I have been considering a CPU cooler, but limited space with my rig's case.

Is it safe to run with 80 deg C for hours (2-3 hours when solving problems)? At what temperature do you usually operate CPU to solve problem?

It looks like I will have to upgrade in a year or two, considering my old motherboard and new motherboard tends to have significant upgrade for connectivity and SSD slots, etc.

Thank you
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Old   February 15, 2017, 12:26
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Great to see that the upgrade paid off.
Finding a "safe" CPU temperature with modern Intel CPUs is easy. If they do not throttle, the temperature is fine. 80C with this CPU is nothing to worry about. Even if the CPU hits ~100C it reduces frequency to avoid damage. Our workstations with the less-than-ideal Dell stock coolers operate 24/7 with CPU core temperatures up to 90C. More about this: https://www.pugetsystems.com/labs/ar...rformance-606/
If the noise from the stock cooler bothers you, there are cheap aftermarket coolers with small form factors that should fit in your case. You just need to know the approximate maximum possible height for the CPU cooler.
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