Linjo,
The host is a Dell PowerEdge R720 with 2 CPU's.
The origional memory, consisting out of 4 * 8 Gb was inserted in banks A1, A2, B1, B2. When installing the additional 4 * 8 banks A3, A4 , B3, B4 were used on top of this. The host boots fine and recognises the memory correctly.
Since the OS keeps rebooting halfway load, just as a test, I removed all memory and inserted 4 identical 16 Gb modules in slots A1, A2, B1, B2. Also in this scenario, the OS does not load.