4 cards [RAM modules] installed, only 2 showing up

Aug 21, 2018
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I recently upgraded from 2x4gb RAM DDR4 2133 (g-skill ripjaw) and added 2x4gb 2666 (same brand) to my ASUS z170k motherboard. The Motherboard manual says it supports different speeds of RAM and DDR4. I have tested all of the RAM sticks on their own and in different orders and none are faulty. BIOS shows I have 4 cards but system information shows only 8gb memory. No idea why this is not working. The cards have been installed in slots 1 & 3, 2 & 4 and vice versa nothing has helped.