After three successful builds you think I'd know its RAM slot 2/4 not 1/2 or 1/3. It's been 10 years and I now just realized I've been doing it wrong. Please roast
4GB DDR3-1333 DIMM | Microseconds
Mac Pro 3,1 2008 RAM Memory Riser Card - 820-2178-B 630-8751 - SR4 Tested | eBay
Mainboard with three RAM slots I found : r/pcmasterrace
How to install ram correctly in X99A Gaming pro carbon - 2x8gb sticks CMU16GX4M2C3200C16 | Overclock.net