ESP-WROOM-02D/02U
Datasheet. pdf 
* a Tensilica L106 32-bit RISC processor. page
* Harvard Architecture. wikipedia
* This device is a 'ESP8266'. The serial command does only support ESP32. -- ESP32 setup. page (Toit firmware)
* We have one ESP32 and 3 ESP8266 (and one missing) to build a Tetrahedron. See also ESP8266 Programming.