Hardware for ANSYS Mechanical - fastest 4 Cores?

Eistee1024 · July 8, 2024, 04:52

Hello everyone,
even though this is a CFD Forum I thought here are plenty of experienced engineers who could give me some advice on hardware for ANSYS mechanical problems

I am limited to 4 cores due to license restrictions and the typical problem does not exceed 64 GB of RAM.

I would go for an AMD 7950X3D or Intel 14900K and the fastest RAM i could get. ECC is not a necessity in my opinion, but I may be wrong. Any suggestions here?

The IT department is not a fan of custom build PCs and preferes HP or DELL builds.

I looked at the gaming PCs there that (HP Omen or Alienware) which at least have the faster CPUs and lower core counts, which is fine since I am limited to 4 cores anyways.
Any hints here?

flotus1 · July 8, 2024, 07:36

The Ryzen 7950X3D should be avoided for your use-case. The extra L3 cache only sits on one of the two CCDs. This way, AMD can advertise both high frequency and high amounts of cache. The best way for you to use this CPU though is running only on the CCD with the additional L3 cache.
That's essentialy the cheaper 7800X3D. Without having to worry about thread placement, or hoping that the scheduler gets it right automatically.

Main benefit of an Intel CPU like the 14700k would be the ability to run higher memory transfer rates without much hassle.
Problem is, you don't get that from HP or Dell/Alienware. They are notorious for speccing the slowest possible memory for their systems, sometimes even slower than the worst memory you can buy anywhere in retail.
14900k just adds more efficiency cores, which you don't need.

So in the end, if you don't need ECC, I think it's a coin-toss whether to go with a 7800X3D or an I7-14700k.

wkernkamp · July 9, 2024, 10:22

Quote:

Originally Posted by flotus1

......

So in the end, if you don't need ECC, I think it's a coin-toss whether to go with a 7800X3D or an I7-14700k.

I have the 7800X3D and I am happy with it. I have DDR5-6400 memory (two sticks) with it. For settings, I use that XMP/EXPO profile. However, I reduced the multiplier to 62. This means that the memory is running as DDR5-6200. This is easy to do from the bios screen. My CPU will run at 6400, but I am not entirely stable.

The FCLK is 2067, the MCLK and UCLK are 3100. The FCLK is the important setting for the infinity fabric which is the memory bandwidth bottleneck on this CPU. For the other two, you want a 2:3 ratio with FCLK. My FCLK can run 2133 (for 6400). However, the UCLK will be too high causing the issues.

Good luck.

Eistee1024 · July 10, 2024, 17:53

Thank you guys for the input! You gave me some things to google and to read up on. I guess it then all comes down to whats the best overall setup I can find at Dell or HP. AMD 7800X3D builds are pretty rare but so is Intel with decent RAM.

They all come with 1000 € + GPUs I'm never gonna use, but hey, not my money...

Quote:

Originally Posted by wkernkamp

My CPU will run at 6400, but I am not entirely stable. ..... However, the UCLK will be too high causing the issues.

Out of curiosity: are you certain the UCLK is causing the issues? What ram did you get? At 6400 I assume you also didn't bother to get ECC, right?

I ran "fast" DDR4 RAM without ECC for years and only once had a solver issue where it reported some memory problems with checksums
which i blame the missing ECC for. Ran it again and worked fine ¯\_(ツ)_/¯
I am just wondering what your experiences with DDR5 are.

wkernkamp · July 10, 2024, 23:45

I am certain that the UCLK is the problem. You can find people that run MCLK 4000 and UCLK:FCLK 2000:2000. So MCLK can definitely go higher.

I myself ran FCLK higher as well (at 2133) because on the 7000 series the infinity fabric does not have to be in sync with the UCLK. This proves that the FCLK is not the problem either. For OpenFOAM, the higher FCLK is not faster than the 2067:3100:3100 configuration. Apparently there is a slight benefit from the 2:3 ratio.

The memory is rated for 6400, so it is not overclocked at all. I am not the only one who is limited to 6200 for stability. Some people even step back to 6000.

In future, I would like to try FCLK:UCLK:MCLK 2133:2200:4400 to see how it does. That would be DDR5-8800. buildzoid has run DDR5-8000 using 2000:2000:4000 see his youtube channel Actually Hardcore Overclocking.

July 8, 2024, 04:52	Hardware for ANSYS Mechanical - fastest 4 Cores?	#1
Eistee1024 New Member Holger Join Date: Oct 2015 Location: Germany Posts: 4 Rep Power: 10	Hello everyone, even though this is a CFD Forum I thought here are plenty of experienced engineers who could give me some advice on hardware for ANSYS mechanical problems I am limited to 4 cores due to license restrictions and the typical problem does not exceed 64 GB of RAM. I would go for an AMD 7950X3D or Intel 14900K and the fastest RAM i could get. ECC is not a necessity in my opinion, but I may be wrong. Any suggestions here? The IT department is not a fan of custom build PCs and preferes HP or DELL builds. I looked at the gaming PCs there that (HP Omen or Alienware) which at least have the faster CPUs and lower core counts, which is fine since I am limited to 4 cores anyways. Any hints here?

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July 8, 2024, 07:36		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,426 Rep Power: 49	The Ryzen 7950X3D should be avoided for your use-case. The extra L3 cache only sits on one of the two CCDs. This way, AMD can advertise both high frequency and high amounts of cache. The best way for you to use this CPU though is running only on the CCD with the additional L3 cache. That's essentialy the cheaper 7800X3D. Without having to worry about thread placement, or hoping that the scheduler gets it right automatically. Main benefit of an Intel CPU like the 14700k would be the ability to run higher memory transfer rates without much hassle. Problem is, you don't get that from HP or Dell/Alienware. They are notorious for speccing the slowest possible memory for their systems, sometimes even slower than the worst memory you can buy anywhere in retail. 14900k just adds more efficiency cores, which you don't need. So in the end, if you don't need ECC, I think it's a coin-toss whether to go with a 7800X3D or an I7-14700k.

July 10, 2024, 23:45		#5
wkernkamp Senior Member Will Kernkamp Join Date: Jun 2014 Posts: 365 Rep Power: 14	I am certain that the UCLK is the problem. You can find people that run MCLK 4000 and UCLK:FCLK 2000:2000. So MCLK can definitely go higher. I myself ran FCLK higher as well (at 2133) because on the 7000 series the infinity fabric does not have to be in sync with the UCLK. This proves that the FCLK is not the problem either. For OpenFOAM, the higher FCLK is not faster than the 2067:3100:3100 configuration. Apparently there is a slight benefit from the 2:3 ratio. The memory is rated for 6400, so it is not overclocked at all. I am not the only one who is limited to 6200 for stability. Some people even step back to 6000. In future, I would like to try FCLK:UCLK:MCLK 2133:2200:4400 to see how it does. That would be DDR5-8800. buildzoid has run DDR5-8000 using 2000:2000:4000 see his youtube channel Actually Hardcore Overclocking.