Full memory encryption. Set a chip on the memory buss, it encrypts/decrypts all the data as it passes between the CPU and RAM chips. At first this would be something like old MMUs before they were built into the CPU itself. They sit on the address bus and add/subtract offsets. This would sit on the data bus and do some simple crypto. Put a capacitor right next to it, first time the chip powers up it selects a random key, when the motherboard looses power the capacitor keeps the chip running long enough for it to overwrite the key that it was internally storing.
Then if they manage to break into your super secure datacenter, wheal in their tank of liquid nitrogen and pump your server full of it just so they can steal your RAM chips...it still doesn't get them anything.
(If you read the paper, they talk about how if you cool the chips with liquid nitrogen they keep their contents with power off and removed for 'several hours'...they argue that simply modifying the bios to zero at startup isn't sufficient as they may physically *remove* the ram chips before you have a chance to zero them)