Dell PowerEdge C8220 Hardware Owner's Manual page 76

Option
Memory Operating Voltage
(Auto default)
NUMA Support
(Enabled default)
Memory Mapped I/O
(Auto default)
Memory Refresh Rate
(X1 default)
76
Using the System Setup Program
Description
If set to Auto, the system sets the voltage to an optimal
value based on the capacity of the installed memory
modules. You can also set the voltage of the memory
module to a higher value (1.5 V) provided that the
modules support multiple voltages. Options are [Auto],
[1.5 volts], and [1.35 volts].
NOTE:
BIOS will auto restrict selection if DIMM is not
supporting low voltage.
Enables or disables Non-Uniform Memory Access
(NUMA) support to improve processor performance.
NOTE:
This option is available for NUMA systems that
allow memory interleaving across all processor nodes.
Select the base address register for the PCIe memory
space. Options are [Auto], [32-bit], and [64-bit].
Enables or disables the 2X memory refresh rate.