My old 486 fails to boot with the 2.6.24-rc1 kernel.
Grub loads it, 4 lines of text appear but not the kernel's
"Linux version <blah> greet", and the machine reboots.
Double-checked with a serial console: nothing appears
before it reboots.
All 2.6 kernels up to 2.6.23 worked fine on this machine.
Config is at http://user.it.uu.se/~mikpe/linux/tmp/486-config-2.6.24-rc1.
The kernel is unpatched 2.6.24-rc1 compiled with gcc-4.2.2.