Built a pc with a 5700x3d b550 tomahawk and 3600cl14 ram. It only posted with ram in slots A1 and A2. I have tried all slots alone and no B channel boots. I did update the bios and saw no bent pins. Since building it i have taken it apart and returned the mobo and got a new one. Did see a post about the 5700x3d having a bad memory controller. I do have a 5700x non 3d that worked in a previous system with that ram.