[hami11]

Hey everyone,


I am looking to buy a desktop for CFD and my choices are between the 7700x (ddr5-6600) and 12600k (ddr5-4800). The 7700x is about 1500 while the 12600k is about 1100. Is it worth the extra amount to get the 7700x?

[wkernkamp]

Originally Posted by hami11

Hey everyone,


I am looking to buy a desktop for CFD and my choices are between the 7700x (ddr5-6600) and 12600k (ddr5-4800). The 7700x is about 1500 while the 12600k is about 1100. Is it worth the extra amount to get the 7700x?

Short answer: yes, because faster by at least 33%.



1. The 7700x has more bandwidth (by a factor 6600/4800 = 1.375) and in CFD this a potential bottle neck.
2. The 7700x has a larger cache (by a factor 32MB/20MB = 1.6) this reduces the load on the RAM bandwidth as data doesn't need to be swapped in and out as much.
3. The 7700x has more performance cores (by a factor 8/6 = 1.333). The 7700x has the additional bandwidth to feed the two extra cores including the slightly higher turbo frequency. I am assuming the IPC for the two processors is equal here.



Note that the efficient cores on the 12500k run at 3/4 the speed of the performance cores. Without complicated uneven sized domains, these cores will cause the performance cores to wait every iteration for the efficient cores to complete their work.

[Habib-CFD]

There are many budget B660-DDR5 boards with 5600(JEDEC) MHz overclock capability of RAM.

The DDR5-5600 kits with Cl28 to Cl40 are available in the market. I feel the total price of the system is determinant, and with the same price the blue team is ahead! A light air-cooler like AK400 completely support 12600K with out thermal bottleneck. The IPC of Intel 12th and 13th gen, and also AMD Zen 4 are almost similar, the higher frequency will affect your scale uplift.

[wkernkamp]

Originally Posted by Habib-CFD

There are many budget B660-DDR5 boards with 5600(JEDEC) MHz overclock capability of RAM.

The DDR5-5600 kits with Cl28 to Cl40 are available in the market. I feel the total price of the system is determinant, and with the same price the blue team is ahead! A light air-cooler like AK400 completely support 12600K with out thermal bottleneck. The IPC of Intel 12th and 13th gen, and also AMD Zen 4 are almost similar, the higher frequency will affect your scale uplift.

No, 6600 is still more than 5600. You did not challenge the other factors. Red is ahead in performance for CFD, Blue has the somewhat lower price.

[Simbelmynë]

Originally Posted by hami11

Hey everyone,

I am looking to buy a desktop for CFD and my choices are between the 7700x (ddr5-6600) and 12600k (ddr5-4800). The 7700x is about 1500 while the 12600k is about 1100. Is it worth the extra amount to get the 7700x?

You can expect this performance from the 12600k, assuming you have the same memory and settings.



It is difficult to state what performance you will get with the 7700x. If you have DDR5 6600 CL32 or CL34, then it will most likely be faster than the 12600k.


Note that both platforms have problems with temperatures. In the Intel case, the CPU can bend due to the non-square shape having incompatibility with old CPU coolers. In the AMD case, the CPU heat spreader is less than ideal and can cause issues, together with aggressive power settings that can cause the stock behavior to send the CPU temperature to 95 oC under load. There are many guides on how to under-volt the CPU though so that is always an option.