Final answer:
The most user-configurable part of the system memory setup is the memory allocation settings in the computer's BIOS.
Step-by-step explanation:
The part of the system memory setup that is most user-configurable is the memory allocation settings in the computer's BIOS (Basic Input/Output System).
In the BIOS, users can typically adjust the amount of memory allocated to the integrated graphics, the memory speed and timings, and enable/disable features like XMP (eXtreme Memory Profile) or A-XMP (AMD eXtended Memory Profile).
For example, if a user wants to allocate more memory to the integrated graphics for better gaming performance, they can access the BIOS and adjust the allocation settings.