Please see this note for more on non-x86 hardware.
IDT Winchip C6-PSME2006A processors are supported under Linux.
The Transmeta Crusoe processors are supported.
Linux has built-in FPU emulation if you don't have a math coprocessor.
Linux supports SMP (multiple CPUs) in all 2.x kernels. See the Linux SMP HOWTO for more information.
ULSI Math*Co series has a bug in the FSAVE and FRSTOR instructions that causes problems with all protected mode operating systems. Some older IIT and Cyrix chips may also have this problem.
There are problems with TLB flushing in UMC U5S chips in very old kernels. (1.1.x)