[jerf]

http://en.wikipedia.org/wiki/Cold_boot_attack

I don't specifically know the answer to your first question if the VRAM is not DRAM (shared memory), but certainly rebooting will not simply automatically clear out DRAM.

[binbash]

shutdown clears, reboot doesnt.

[nitrogen]

Shutdown actually doesn't clear RAM, hence the "cold boot attack" terminology. Eventually the data will degrade, but eventually can be a long time.

[binbash]

Yeah. My comment was ment to answer the question above yours...