BIOS does not see RAM, but Windows does. What's the matter?

Question

laptops

The laptop had two 4 GB sticks, then one of them died. Bought an identical replacement. And now, at startup with two bars, the BIOS does not see a new bar, but Windows sees them, only reports that only half can be used. The bar itself is 100% working - tested on another computer. Bios update didn't help. Where to dig further? There is a discrete video, a BGA processor, the laptop was not dropped.

Answer 1

Alternatively, try swapping them. Or maybe the previous one didn’t just die, but the problem is in the laptop itself? I think it is better to contact a competent service with this issue.

Answer 2

incompatible boards.
try separately for performance and at the same time look at the SPD records in each plank.