My weird issue with this Toshiba laptop

[lVaderl]

So i have a Toshiba latitude P755 and it comes with 6 gbs of ram in a 4 gb stick and a 2 gb stick (both clocked at 1333 mhz)

I have a 4 gb from a lenovo laptop (idea pad somthing XD) thats clocked at 1600 mhz

 

When I try changing the 2 gb stick on the toshiba to the 4 gb stick, im able to boot into bios and I can see the Bios can see all 8 gb of ram no problem

but when i try to boot into windows or anything eles (memtest and liniux) i get a black screen with a blinking underscore at the top left 

 

Note im able to boot just the old 4 gb stick, but with the lenovo 4 gb stick the laptop didn't even turn on 

also swapping the toshiba and lenovo ram sticks to see if different slots also made the laptop not turn on

 

(by not turn on = not able to boot into bios)

 

Any help would be nice :D

[Nord]

You probably need to set the ram to the same settings within the bios. MHZ, Cas latencys and so forth.

Boot them one by one and check in CPU-Z what settings they can support (or do it from the sticker if its on there)

 

Also not all ram are always compatibly with each other, it might also just boils down to this.