Yeah, semi-passive. Arctic has been showing a new prototype CPU cooler for AMD's Threadripper processors. The cooler rather ginormous and named 'Freezer 50 TR". Arctic claims it should be able to passively cool a Threadripper-CPU under low load. 

The wording semi-passive thus is rather misleading, as under load the fans simple kick in and the product will behave like a normal cair based heat pipe cooler. The Freezer 50 TR has two aluminum cooling blocks, each with eight heatpipes in direct contact with the processor.

The cooler can hold two fans (we assume 140 mm. Of course, there's some colorful RGB stuff going on as well. Price and availability have not been mentioned, obviously as it is a prototype.

Arctic shows semi-passive Freezer 50 TR cooler for AMD Threadripper