what is MMU
 

Was reading a howto, and it says:

Since the IXP425 has an MMU, we can use glibc. No need to use one of the other libc libraries.

Than I do a google search:

MMU, short for Memory Management Unit, is a class of computer hardware components
responsible for handling memory accesses requested by the CPU. Among the functions
of such devices are the translation of virtual addresses to physical addresses
(i.e., virtual memory management), memory protection, cache control, bus arbitration,
and, in simpler computer architectures (especially 8-bit systems), bank switching.

My question is:
1. where does MMU locate on a computer? in the CPU? on the mother board?
2. why would MMU have any effect on which libc we use... I mean if we don't have MMU are we forced to use other c library like uClibc

The MMU is a part of the CPU. And if you don't have MMU, the software have to make explicitly address translation (as if you don't have FPU, you have to emulate it by software). That's why you have to use a specific kernel and libc (in wich address managements are made software way) for this kind of system