Most of the RIFTs robots use compact nuclear power plants giving them a selfcontained power supply for a number of years, usually 15 to 20 years. This assumes that up until the time of RIFTs, mankind had not successfully integrated fusion power, and that nuclear was deemed safer for use in the type of battle machine stipulated, or that after the time of RIFTs, mankind simply fell back onto proven knowledge, and rebuilt from existing materials. This also assumes that the cost and value of life is much lower in RIFTs than in the real world, proven by the very chaotic style presumed in the game system itself.
The robots move using most likely, plasticised musculature that is a form of memory material. It has two states, charged and uncharged, and when energised, will contract; as the charge fades, it will expand again, enabling the robot's muscles to work like human muscles, and allowing good freedom of movement.
Sensors and other equipment in the robot are simply extensions of current technology, with radar, infra-red sensors, motion detectors, all able to be extrapolated using current technology.
The computer controls however, are another thing. even the most powerful systems currently available today would seem horribly inefficient compared to the control systems for even a simple robot system like the SAMAS or Glitterboy. To miniaturise something like a Cray or a Silicon Graphics workstation to the size required would take a quantum leap in processor manufcture and the use of nano-technology to construct and configue the equipment. Also, room temperature superconductors are not unlikely given the apparent ease of which power is flung about the robots' systems.