I don't know if the following has been done, but here goes:
Would it be advisable to provide a DC-DC power supply (PS) to an ATX system for the purpose of;
1) Increased efficiency
2) Decreased heat
3) Decreased fan noise If you used an automotive style sealed battery in the circuit and a trickle charger, wouldn't you also provide a fairly substantial UPS system ? I've seen DC-DC power modules that plug directly into the ATX power connecter the size of a playing card. DC Regulated Switching Power Supplies are not too expensive if you're trying to meet the above criteria.
I believe that the computer industry has not utilized the DC-DC PS because of the ubiquitous $50 PC AC-DC Internal PS. If I'm way off on my ideas, please advise. If you can shoot holes in my ideas please do so.
TIA, Trent M. Gunnarson