data persists in DRAM even without power

[Jonathan]

http://www.boingboing.net/2008/02/21/re ... rypti.html

My own experiments in disabling DRAM refresh indicate that the machine can keep humming along for twenty seconds before a fatal error occurs without refreshing the DRAM at all. If you're willing to tolerate a high fault rate, several minutes sounds like a perfectly reasonable window to extract useful data from recently used DIMMs.

[Jason]

What would be a "safe" amount of time?

[Jonathan]

http://citp.princeton.edu/memory/faq/

I certainly haven't attempted to defeat any security or encryption. I defer to the authors of the paper, who say several minutes in the powered off state should suffice.