Cooling a large microprocessor in a small module

A modular computer with docking bays for receiving functional modules and connecting the functional modules to internal computer circuitry has translatable heat-sink structures for contacting docked functional modules to extract waste heat generated by operation of the functional modules. The structures are mechanically actuated to retract to provide clearance for insertion and withdrawal of functional modules, and to advance to contact modules when docked. Heat-sink structures are shaped in some embodiments to securely retain docked modules, and in some instances, the translation of the heat-sink structures is by electrically operable actuators, which may be actuated by signals from a CPU of the modular computer. In these instances, the computer may be configured to require a security code or special input sequence to retract the heat-sink structures allowing a module to be removed.