I for all. I use Windows 10 1903 ad Adrenaline Driver version 19.9.2. When Crossfire is on and I start same games (I using Knights of the Old Republic Battlefront II) or benchmark (3DMark) I obtain a system freezing and reset is necessary. After restart "Default Radeon WattMan settings has been restored due to unexpected system failure", even if I didn't make any changes. If Crossfire is off, then all work fine. This problem does not occur in Windows 7.
My system configuration:
mainboard: Asrock Extreme 3
processor: AMD Phenom II x4 955
installed RAM: 16GB DDR3
graphics adapter: 2 x Sapphire Radeon RX 570 Nitro+
power: Tacens Anima APII750 (750W) with splitter from 6PIN in to 2x8 (6+2) out PIN