AMD UCLK DIV1 Mode enables forcing the memory controller to run at the same or half the system memory frequency.

uclk div1 mode

On AMD Ryzen processors, UCLK is the term used for the Unified Memory Controller Clock frequency.

On the 1st generation Ryzen processors, UCLK runs by default at the same frequency as the system memory and the fabric frequency. From the 3rd generation Ryzen processors, users could run the fabric, memory controller, and memory frequency in asynchronous mode.

The memory controller can either run at the same or half the frequency of the system memory. The user can force either by configuring the UCLK DIV1 Mode option. Thus, the maximum frequency is limited to the maximum supported memory ratio by the Ryzen processor. On Raphael processors, that’s up to 6000 MHz with the DDR5-12000 memory ratio.