Port 70h is where it went in the AT (which is what most people are probably referring to when they say "PC compatible" these days.) On the PC and XT, it's in port A0:
Thre's also another set of NMI control bits in port 61h on an AT. It's worth noting that the port 70h and 61h controls are still there in the 2022 Intel 600-series chipsets, almost 40 years later; look at pages "959" and "960" of this: https://cdrdv2.intel.com/v1/dl/getContent/710279?fileName=71...
