GSIC TSUBAME 2.5 is a large GPU cluster operated by Tokyo Institute of Technology, located in Japan, in the public sector. It came online around June 2014. At that moment it ranked number 3 among known clusters.
It is built on 4,224 NVIDIA Tesla K20X. That amounts to about 8.4 H100e of AI compute. The cluster draws roughly 2.69 MW. Its hardware is estimated at $63M.
Epoch AI rates the certainty of this record as confirmed. 1408*3 = 4224 Top500 implies that there are at least 4140