We're using the E3-1275v5 processor with Kingston 8GB DDR4 DIMMs. The Kingston pn is KVR21E15D8/8. I have checked the jumpers and cables and those look O.K. I took the DIMMs out and then the system responds with 3 long beeps that says I have a memory error. So that part works and it appears the processor is alive. I checked the diagnostic LEDs. If I am reading them correctly, it appears the system stops on 4Fh. Also, the blinking LED next to the 8 diagnostic LEDs goes from blinking green to a solid amber. Then after a short time the machine reboots.