Amount of RAM does not add up

[Tim Hutchinson]

Hi All,
I have an Asus B350Prime mobo, with two 4GB sticks of DDR4 ram, but I am getting very mixed reports on the total ram.

• BIOS says 4GB in slot A2, 4GB in slot B2. Total memory = 4GB
• Windows (W10 pro) reports 8GB total, but only 3.94 usable
• memtest only finds 4GB

Any body come across this before, or could offer any advice?

 

[Tim Hutchinson]

Windows reports 64bit os and 64bit cpu (system properties screen). Could this be wrong?
If I boot to usb and run memtest it does not produce any errors but only finds 4gb ram. Surely booting to usb like this would eliminate a fault with the os?