I have a S2600CP with 2 e5-2670. when I received the motherboard, I booted it to check CPU and RAM and worked fine.
Now, 2 weeks later as I'm assembling the server, the motherboard powers on for a second, then powers off(all fans spin for a second), if left untouched it will sporadically try too boot for a second and shut off(in a loop).
I tried to remove CPUs and RAM and it beeps as expected complaining for the CPU.
I removed the motherboard from the chassis.
With a single CPU it behaves the same way, same with just one or two sticks of RAM.
I tried a different power supply with the same result.
I changed the CMOS battery and reset the BIOS.
If I power up with the BIOS jumper set to "reset to defaut" and then boot, it beeps with 1-5-4-2 that is DC power loss.
All the PSU I have tested are 850W.
thank you for your time