DL580 G7 not booting / posting

I have two DL580 G7 and I cannot get any of these to boot.

What happens is that the internal health LED flashes red and it displays all four CPU-LEDs in amber. There is no post code, exactly nothing at all on the VGA. Just plain black.

What I did so far:

• I removed all RAM-cartridges and CPUs except for one of each.
• I swapped them with eachother.
• I tried out different type of CPUs (I have a set of Xeon E7540 and a set of Xeon E7-4830).
• I tried a different DL580 G7 with the CPUs and memory.

So I basicly changed everything except for the RAM, because apart from these four cartridges (6x4GB each, which I of course swapped and tried out in different combinations) I do not have any other server memory here.

I can get into ILO 3, but it is displaying wrong information about my system. It will always state that there are four 10 core-cpus installed (which is not true) and it is also always giving wrong information about the memory. It does however display the fans and PSUs correctly.

Resetting the NVRAM didn't help. I am really confused because the exact same problem with the same symptoms occurs on both the machines. Before I go and buy new ram (which is expensive), is there any other trick that I could do?