Which device limits the maximum amount of RAM in the motherboard?

Question

motherboards

The following configuration is used as an example:
Processor: Intel Core 7-8700K: - Max Memory Size (dependent on memory type) 64 GB
Motherboard: ASRock Fatal1ty Z370 Gaming-ITX/ac: - Max. capacity of system memory: 32GB
We have a processor with a built-in RAM controller that supports more RAM than the motherboard.
Is the motherboard really limited to 32GB, as the manufacturer indicates, because the northbridge built into the CPU works with 64 GB and, logically, the motherboard should work with this maximum volume.
If there is a limit, then what limits it, the chipset, BIOS or some other component affects the limit, how the motherboard manufacturer limits it.

Answer 1

The memory controller in the processor and limits. The datasheet on pages 19-20 describes the supported modules - there are no modules of 32GB each, the maximum processor can do is 4 DIMMs of 16GB each = 64GB.
And on the specified motherboard, there is simply nowhere to insert so much memory - there are only two slots instead of 4, for which the maximum supported volume is calculated.

Answer 2

Memory controller and chipset. The chipset "regularly limits the capabilities of the controller - such a bastard. More precisely, this is the" fault "of the chipset manufacturer, which made such a limitation. Although, on the other hand, sometimes this limitation is paper or with conditions, but in reality, there are some possibilities to use the maximum supported volume, but you need to read about specific pieces of iron, but of course I won’t do this, I suggested the direction of the search, I think that’s enough;).