3 Things to Know About Registered ECC in an HP Z420

Registered ECC (RDIMMs) will not work in an HP Z420 The motherboard is locked to unbuffered ECC (UDIMMs) only, and the memory controller will not train or boot with registered modules.

The CPU can handle both, but HP restricted the board Xeon E5 v1/v2 processors technically support registered memory, but HP’s firmware limits the Z420 to unbuffered sticks. A specific firmware revision might work, but it is not reliable.

Stick with unbuffered ECC sticks for guaranteed compatibility Use PC3-12800E or PC3-14900E unbuffered ECC memory. If you need more than 64GB, this workstation is not the right choice.