I've been testing the AMD Ryzen 5 3600x CPU on two different ASUS motherboards and have come to the conclusion that it is incapable of running RAM at full speed in slots A1+B1. It can only run at full speed in slots A2+B2.
I've tried updating to the latest BIOS and playing with such settings as D.O.C.P which helps slots A2+B2 run at full speed but not A1+B1.
Here are the motherboards I've tested:
ASUS ROG STRIX B450-F GAMING
ASUS TUF B450-PLUS GAMING AM4
Here are the RAM models I tested (always tested separately with same RAM model, never mixed):
G.SKILL Trident Z RGB (For AMD) 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800) Desktop Memory - Model F4-3600C18D-16GTZRX
TeamGroup T-FORCE VULCAN Z 32GB (2 x 16GB) DDR4-3200 PC4-25600 CL16 Dual Channel Desktop Memory - Model TLZGD432G3200HC
Here are my results:
G.SKILL - slots A1+B1 - 2133MHZ
G.SKILL - slots A2+B2 - 3600MHZ
G.SKILL - slots A1+A2+B1+B2 - 2133MHZ
Teamgroup - slots A1+B1 - 2400MHZ
Teamgroup - slots A2+B2 - 3200MHZ
Teamgroup - slots A1+A2+B1+B2 - 2400MHZ
Is this a limitation of the AMD Ryzen 5 3600x CPU or with ASUS motherboards?