[oj.bulmer]

I need a bit of help in deciding the configuration and correct pricing for the PC:

Quote 1: This one is with processor “Intel i7 4930K Unlocked (6 x 3.4 GHZ)”
Computer Case: Black ATX Tower Case
CPU: Intel i7 4930K Unlocked (6 x 3.4 GHZ)
CPU Cooling: Intel Heatsink & Fan - Low Noise
CPU Compound: Standard CPU Compound Supplied With Heatsink
Memory: Corsair Vengeance LP 32GB 1866 MHz (4x8GB) - Lifetime Warranty (DDR3)
Graphics Card: 1 x NVIDIA GeForce GTX 750 - 2GB - (EVGA) - Superclocked - (PCI-E)
Power Supply: Corsair 450W PSU - Low Noise
Motherboard: Asus P9X79 (Intel X79)
Hard Drive #1: 1 TB Seagate (1000 GB) SATA-III HDD 7200 RPM 64MB
Operating Systems: Microsoft Windows 7 Professional 64 BIT (Genuine DVD & COA Included)
Monitors: 1 x 24" HD LED Widescreen Monitor - Black - 2ms - 1920x1080 - DVI/VGA
PRICE: £1453

Quote 2: This one is with "Intel i7 4930K Unlocked (6 x 3.4 GHZ) OVERCLOCKED UPTO 4.4 GHZ" and as a result of this overclocking, the first three components (highlighted in red) need to be changed due to compatibility issues.
Computer Case: Aerocool X-Predator X1 Devil Red
CPU: Intel i7 4930K Unlocked (6 x 3.4 GHZ) OVERCLOCKED UPTO 4.4 GHZ
CPU Cooling: Coolermaster Hyper 212 Evo - Low Noise
CPU Compound: Standard CPU Compound Supplied With Heatsink
Memory: Corsair Vengeance LP 32GB 1866 MHz (4x8GB) - Lifetime Warranty (DDR3)
Graphics Card: 1 x NVIDIA GeForce GTX 750 - 2GB - (EVGA) - Superclocked - (PCI-E)
Power Supply: Corsair 450W PSU - Low Noise
Motherboard: Asus P9X79 (Intel X79)
Hard Drive #1: 1 TB Seagate (1000 GB) SATA-III HDD 7200 RPM 64MB
Operating Systems: Microsoft Windows 7 Professional 64 BIT (Genuine DVD & COA Included)
Monitors: 1 x 24" HD LED Widescreen Monitor - Black - 2ms - 1920x1080 - DVI/VGA
PRICE: £1558

I have two questions:
1) Is the configuration (6 cores, 32 GB RAM etc) alright to comfortably run CFX/FLUENT? It would be mostly used for porous regions, vortex shedding analysis and a multiphase simulations, covering both steady and transient simulations.
2) Is the £100 increase in configuration due to overclocking reasonable?

Thanks a lot!

OJ

[singer1812]

Did you look up the difference in the case and CPU cooler separetly? That is essentially what you are paying for.

The motherboard/cpu is the same in both cases, so you could overclock this yourself. But you have to worry about the cooling, which I assume they did correctly for that speed.

[ghorrocks]

Be aware that CFD loads the CPU very highly for long periods of time so you will be really loading this overclocked system. And it also heavily loads the memory pipeline, FSB and a few other bits of the motherboard as well. It is not just the CPU. I would not consider an overclocked system for CFD work.

Sure, you can overclock and it runs fine most of the time. But I am just thinking about having to face the CEO and say "The simulation failed and I fried the computer because I tried to squeeze a bit of overclocking out of it." It might be boring using stock computers but at least if they go wrong it is a straight-forward warranty issue.

But that's just my opinion. Feel free to overclock if you feel brave

[Antanas]

Why do you need overclocked gaming graphics? IMO Quadro series is better choice. And I agree with Glenn about CPU overclocking. You'd better not overclock it and then you can buy not unlocked version which must me cheaper. Also i7 has turboboost technology so it can auto overclock if not all cores are used.

[oj.bulmer]

Did you look up the difference in the case and CPU cooler separetly? That is essentially what you are paying for.

I have generated these quotes from one of custom PC building websites online. The difference is actually due to the computer case and the Coolermaster cooling.. oh and yes, the "overclocking tax" that the PC makers will charge of course

But I am just thinking about having to face the CEO and say "The simulation failed and I fried the computer because I tried to squeeze a bit of overclocking out of it."

Yes! This is what I fear. I have seen both CFX and FLUENT push the boundaries of hardware configuration which would make the CPU run at overclocked speed for sustained periods of time. Well, I voiced out this concern to the online advisor and his response was "It should be OK." Obviously he was playing by the script and hasn't run many CFD simulations! I have read that overclocking doesn't necessarily add to the speed of solution CFD, but memory speed (MHz) does. Would it be wise to to for 32 GB 2400 MHz RAM than 1833 MHz that I have currently chosen, keeping the processor unlocked, instead of overlocked?

Why do you need overclocked gaming graphics? IMO Quadro series is better choice

I agree, but I thought I should get more juice from CPU, RAM, motherboard and going cheap on the rest...

[oj.bulmer]

Also, I was wrestling with the choice for the processor. I have read that opting for overclocked CPU versus normal unlocked CPU doesn't really add much benefit when it comes to solution times, is it true?

Also, my current configuration is 6 core processor. Would going for a standard 4 core processor (with a bit high frequency) be better? Is the performance boost going from 4 to 6 core significant?

Thanks

[ghorrocks]

Your best bet for getting performance information on CPUs is at www.spec.org. The raw benchmark is effectively the single processor performance, and the rate is the multi-processor performance so you can work out the scaling effectiveness from that.

In most commercial license cases it makes sense to purchase a smaller number of licenses and get the fastest CPU possible - so less cores, more speed. In fact license costs usually swamps computer cost so it often makes economic sense to only use 1 or 2 cores on a PC and do distributed parallel across several PC. This was certainly the case several years ago by multicore operation has improved a lot recently and things have hopefully improved.

You know what I will say about overclocking.... I have already said it. It is not worth the risk. But if you can handle a bit of risk and some simulations dying due to stage overclocking behaviour then go for it.

[Antanas]

Originally Posted by oj.bulmer

Also, I was wrestling with the choice for the processor. I have read that opting for overclocked CPU versus normal unlocked CPU doesn't really add much benefit when it comes to solution times, is it true?

Also, my current configuration is 6 core processor. Would going for a standard 4 core processor (with a bit high frequency) be better? Is the performance boost going from 4 to 6 core significant?

Thanks

I think the number of cores depends on the problem. Here info from CFX help:

Do Not Run Small Jobs in Parallel

For tetrahedral meshes, you may want to use a minimum of 30,000 nodes per partition. For partitions smaller than this, you are unlikely to see any significant performance increase and may even see parallel slow down.

For hexahedral meshes, good parallel performance improvements are usually not seen until a minimum of 75,000 nodes per partition is reached.

Try to Use a Sensible Number of Partitions

The partitioning of a mesh leads to the creation of overlap regions at the partition interfaces. These regions are responsible for communication and memory overhead during a parallel run. During partitioning, ANSYS CFX prints partitioning diagnostic information to the CFX-Solver Manager text window and output file about partition overlaps. The percentage of overlap nodes to the total number of mesh nodes should ideally be less than 10% for efficient partitioning. Values greater than 20% will impair performance and are not recommended.

I think this info may help you to decide. Note that you should give at least one core for OS needs.