I have an eeepc with Intel Atom N270. Using grsecurity-2.2.2-2.6.32.41 the kernel boots fine. The next I tried was grsecurity-2.2.2-2.6.32.51. This one fails to boot right in the first part of the bootprocess, printing unreadable lines of text on the screen indefinetely. The same Kernel boots on a core2 just fine.
I compiled with gcc-4.5.3, trying both atom and 386 as processor type in menuconfig.
An non grsec patched Kernel boots fine on the Atom.
Unfortunately I have not enough knowledge of the bootprocess to look into the changes from 2.6.32.41 to 2.6.32.51 myself.
Thanks for hints,
thorsten