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In this case bear in mind that the manufacturers (Dell, HP, Asus, etc) can limit or restrict some features so they can fit with their system. This means that even if the RAM can go up to 4800MHz if the motherboard only supports up to 3600MHz they will limit the speed.
On the other hand, there is an option at the BIOS called Intel® Extreme Memory Profile (Intel® XMP) that allows you to overclock the RAM by selecting different profiles (speeds). we do not recommend overclocking the RAM since this can damage the CPU.
My advice is to get in contact with Dell to confirm if the RAM speed is limited or if you are able to change it.
Please keep in mind that this thread will no longer be monitored by Intel.
Intel Customer Support Technician
To add some additional information, my experience has been that it is the motherboard that also needs to support certain types of RAM. So if the motherboard (and of course the BIOS) does not support DDR5 RAM, then you are out of luck regardless of the speed.