XPS 8960, Crucial Pro ram 5600MHz running at 5200MHz

While it's nice to squeeze every ounce of speed from components, that is not a huge deal IMO.
My 8950 shows only 4400MHz so maybe Dell has throttled it with a BIOS update.
That module is listed as compatible so that's good.
Maybe you can tweak with Intel's Extreme Tuning Utility?
It might only do CPU but might be nice to tweak with.
While your 8960 is a killer setup, keep in mind that a Dell XPS prebuilt is compromised a bit and you will not easily get maximum performance from it.
An Alienware R16 might be a bit better but still, these systems have heat and power restrictions.
I have to know what display you chose, and I hope it's worthy! :)

Try to look inside the BIOS and see if there is any xmp or manual adjust memory timing section. You should be able get it adjusted there. 

Sometimes Dell sells PCs with RAM that's faster than the motherboard/chipset actually support.

The XPS 8960 specs say it can use 4800 and 5600 MHz RAM, but doesn't explicitly say it will run the RAM at those speeds. Install CPU-Z (free) and see what it reports for RAM speed. And while in CPU-Z see what it reports for "Channel #", single or dual, or 1x 64 bit or 2x 64 bit.

BTW: Did you try resetting BIOS to make sure it is seeing the new RAM correctly?

1. Reboot and start tapping F2 when you see the Dell splash screen to open BIOS setup
2. Copy down all current BIOS settings, to be safe
3. Power off, unplug power cord from rear of PC
4. Press/hold power button for ~15 sec
5. Open case and remove motherboard battery (check Service Manual for details)
6. Press/hold power button for ~30 sec
7. Reinstall battery
8. Close up and connect mouse, monitor and keyboard
9. Reboot, open BIOS setup again and verify all settings match what you copied, or change to match. Save changes, if any, and exit setup. PC will boot automatically.
10. Check RAM speed again.

@Socom Master​ 

Sorry man but an i9 even with a Dell or Alienware water cooler is a great advancement but don't be fooled.

It's not enough really when you really push the CPU.

All I'm saying is don't sweat the little things with your Dell.

It's a killer system but your thinking implies you have the wrong solution if you want that last 10% of performance.

BTW, I noticed when configuring a Dell/AW PC that the Mem speed is 5200 on 64GB and 5600 with 32GB so maybe that is what you are seeing.

As for the display.....lol....no comment. :P

Hi, can you tell me what version of  BIOS do you have.

Thanks 

Same. Same dell PC and ordered the same Crucial 5600MHz RAM from Amazon (2x32GB). The speed slowed down to 5200MHz. I like this powershell command:
Get-CimInstance -ClassName Win32_PhysicalMemory - it shows this for both chips
Speed                : 5600

...
ConfiguredClockSpeed : 5200

Well what are you going to do? I think the extra capacity will be nice even if it is a little slower. I doubt I'll notice any difference for my workloads

Any solution? So that the memories work at 5600? Or is it a processor limitation?

mine looks like the friend above @mikedice417 

Get-CimInstance -ClassName Win32_PhysicalMemory - it shows this for both chips
Speed                : 5600

...
ConfiguredClockSpeed : 5200