Since you didn't bother describing your config I'm going to assume that you've got AMD Polaris cards. If that's the case, then my guess is that the voltages you set in the BIOS aren't getting applied in SMOS. I don't think I've ever had a Polaris card that just worked the way I wanted by simply editing all the clocks and voltages in the BIOS. Yes, they do get saved there, but if I don't use some kind of extra software to control the clocks and voltages from the OS, the cards don't use the voltage from the BIOS anyway. They do run at the clocks set in BIOS, but the voltages still default to the stock values. So I have to use something like OverdriveNTool and set lower voltages with it.

If you're mining ETH with Claymore's miner, then you could probably control the voltages and clocks with it by setting -cclock, -mclock, -cvddc and -mvddc.