Machine Check Exception support allows the processor to notify the kernel if it detects a problem (e.g. overheating, component failure). The action the kernel takes depends on the severity of the problem, ranging from a warning message on the console, to halting the machine. You can safely select this on machines that do not support this feature
For pentium machines the mce support defaults to off as the mainboard support is not always present. You must activate it as a boot option.
Linux can emulate a math coprocessor (used for floating point operations) if you don't have one. 486DX and Pentium processors have a math coprocessor built in, 486SX and 386 do not, unless you added a 487DX or 387, respectively. (The messages during boot time can give you some hints here ["man dmesg"].) Everyone needs either a coprocessor or this emulation.
If you don't have a math coprocessor, you need to say Y here; if you say Y here even though you have a coprocessor, the coprocessor will be used nevertheless. (This behaviour can be changed with the kernel command line option "no387", which comes handy if your coprocessor is broken. Try "man bootparam" or see the documentation of your boot loader (lilo or loadlin) about how to pass options to the kernel at boot time.) This means that it is a good idea to say Y here if you intend to use this kernel on different machines.
More information about the internals of the Linux math coprocessor emulation can be found in arch/i386/math-emu/README.
If you are not sure, say Y; apart from resulting in a 66 KB bigger kernel, it won't hurt.
This enables support for systems with more than one CPU. If you have a system with only one CPU, like most personal computers, say N. If you have a system with more than one CPU, say Y.
If you say N here, the kernel will run on single and multiprocessor machines, but will use only one CPU of a multiprocessor machine. If you say Y here, the kernel will run on many, but not all, single machines. On a singleprocessor machine, the kernel will run faster if you say N here.
Note that if you say Y here and choose architecture "586" or "Pentium" under "Processor family", the kernel will not work on 486 architectures. Similarly, multiprocessor kernels for the "PPro" architecture may not work on all Pentium based boards.
People using multiprocessor machines who say Y here should also say Y to "Enhanced Real Time Clock Support", below. The "Advanced Power Management" code will be disabled if you say Y here.
Documentation/smp.txt, Documentation/i386/IO-APIC.txt, Documentation/nmi_watchdog.txt and the SMP-HOWTO available at <http://www.tldp.org/docs.html#howto>.
If you don't know what to do here, say N.