They do exist https://www.picocluster.com/collections/pico-5/products/pico.... I have a 5 node Odroid cluster.
The RevPi Core 3 is equipped with a high performance cooler which is able to sustain 1.2 GHz at full load for about 20 minutes (at room temperature). After that the clock rate will be moderately reduced to 1.15 GHz.