May be Front End author should use this post, to specify minimum requirement and a Wiki master can enter it on the wiki ?
Just in case , i Start :
For Atomic the really minimum is a Pentium 1 233Mhz , 32 Mega memory and NO 3d Video Card.
Realistically, to use Atomic more confortably with Static layout in 640x480 , the minimum is Pentium 2 400 Mhz , 64 Mega memory , DirectDraw compatible video Card (no need of Direct 3d).
Then it depends of the complexity of the layout you use and the resolution.