speed up with more cache?
 

Hi everyone,

I got an older workstation I bought to simply get in touch with CFD and playing around.
I got the Dell T7810 full equipped with all RAM Slots and 2x E5-2650v3 Processors.
So far I am happy with my invest.

As the calculation never can get fast enough I think about different ways to do that. The one related is the question if a switch to an 'better' Processor would increase the speed.

In some time before I realised that half of the RAM slots was nearly as fast as fully equipped. Tested with the OpenFOAM motorbike benchmark. So I think there should be more possible.

I had a look to a selection of possible Processors at the link below. All E5-26xxv4 should work.

https://ark.intel.com/content/www/us...70,91772,96901

The retail prices seems to be related to cores/cache. I thought on a cheap invest for the E5-2660v4.
Does anybody know if a switch to a Processor with mor cache will significantly speed up?

Thanks for all tipps and hints.
Best regards
Michael

Honestly this is a pretty hard question as it varies heavily with core architecture. As far as I know, doubling the cache of a processor never gives it more than a 10% increase in power (thinking about Epyc processors right now), so it is nice to maximize cache as long as it is not increasing your budget significantly.

The correlation is not really between MSRP and L3 cache size. For this era of Intel CPUs, L3 cache per core was pretty much constant. So you were paying mostly for the cores.
And yeah, last level cache size matters, but the benefit is rather small. You need a huge increase in cache size to get a meaningful impact. See AMDs Milan-X and Genoa-X CPUs, which triple the amount of L3 cache.

At less than 20€ from Chinese sellers on ebay, the E5-2660v4 is extremely cheap. And it will be a small upgrade. More cores, slightly newer, supports faster RAM.
If you want to spend a bit more, the E5-2697A v4 are still a good deal. In the range of 80€ on ebay.
Whether the OEM workstation supports these newer CPUs with a newer bios version, I don't know.

Thanks for the reply.

I will simply test it for some 100...150 €.
I changed my search in the "OpenFOAM benchmarks on various hardware" thread and found some related pieces to my question.


Best regards Michael

Thanks flotus,

I read your statement after my first reply.
Nevertheless, in the meantime since yesterday I was looking for what I get for which money.

I think it will be the E5-2695 v4. Do you see a big difference to E5-2697A v4? Bios should support it.
I think I will wait till 2024, I do not have the time at the moment. Maybe the prices will change for something better.

Best regards Michael

There are minor differences, but nothing worth worrying about.
The 2697A v4 has fewer cores, but higher clock speeds. Which I generally prefer.
But again, either CPU is fine.

I agree with Flotus here. The changes in cache between processors were minimal in this generation of xeons, and higher clock speeds are generally better than higher clock counts once you get past 12 cores or so (again, for this gen)

Thanks a lot for all the reply.

In the meantime I got the processors and tested them.
I made the motorbike case. Not sure if it is completely comparable with the old test case. I still use it as a comparison on my machine. DIMMs are all full.


For the older E-5 2650v3 I got:
# cores Wall time (s):
------------------------
1
2 418.301
4 191.938
8 113.197
12 83.9055
16 69.1103
20 63.1804


The newer E-5 2697v4 get me:
# cores Wall time (s):
------------------------
1
2 348.798
4 157.442
8 93.1168
12 73.1635
16 58.3126
20 50.4227
24 46.4439
28 43.1391
32 41.4611
36 40.2852


I am happy with that. Got remarkable more power for a invest which was ok for me. I did not thought it would be that much.

Best regards
Michael