Specs below, motherboard is an MSI Z97M. Manual states for dual channel ram you populate DIM2 and 4. So my old ram (Radeon r9 2400mhz 2x4gb) works fine in those slots, but my new ram Dom Platinum 16gb 2400mhz doesn't post in slots 2 and 4, I get a memory error '26'. The new ram DOES, work in slots 1 and 3, with all 16gb detected. Old ram works fine in all slots. So is this a dual channel issue? Will it impact performance? Any ideas how to sort it? Edit: both of the new sticks will work in the following slots on their own : 1,3,4 So slot 2 with either module is the issue, not with old ram though. That works in every slot.