RAM slots 3 and 4 not working: Faulty motherboard?

Sounds like you have either the wrong RAM module or the systems firmware is not up to date (I would be surprised if it's not already

3 and enable lifelike virtual worlds with 3x SSD 4x RAM Slots More Storage More Memory More Expansion The Titan 18 HX features 4 DDR5 memory slots

rams slot receiver To solve this problem, memory bandwidth must scale with the increase in CPU core count Some users have addressed this issue by overclocking their DDR4 memory

ramses book christmas edition slot If that's not an option, try to keep the modules' specs as similar as possible, as every RAM module will run at the same speed as the slowest