Z420 / 256G RAM running on 1600MHz instead of 1866MHz

Hi, I did upgrade CPU and RAM on my HP Z420 Workstation. I have the second version so can use both V1 and V2 Xeon processors. I have the latest bios version J61v03.96.

CPU is now Xeon E5-2697 v2 with supported RAM speed at DDR3 800/1066/1333/1600/1866.

https://ark.intel.com/content/www/us/en/ark/products/75283/intel-xeon-processor-e5-2697-v2-30m-cache-2-70-ghz.html

RAM is now 8x32G LRDIMM 1866MHz (part number M386B4G70DM0-CMA3) with passive cooler

But for some reason, RAM still running on 1600MHz. I didnt find any settings in BIOS to force higher speed.

Any idea how to make RAM run on 1866MHz?

thnx