[SOLVED] Only the 4th dimm slot will work on my Z490 gaming edge

[aPosast]

I can only use 8GB of ram because none of the other slots work. If I plug my other stick in it light up on the debug (dimm for 2 seconds, switches to CPU, and then goes right back to dimm). Both the sticks work in the 4th slot so I know the ram isn’t broken. Ram is 8GB 2666mhz on MSI .z490 gaming edge

 

[mikewinddale]

Probably a defective or failing motherboard. Possibly the CPU (since that's where the memory controller is). But I'm betting on the motherboard.

Call the motherboard manufacturer and ask what they think.