integer arithmetic overflow

Is it defined how integer arithmetic overflows?

For instance, is it guaranteed that adding or multiplying two large unsigned ints will “gracefully” overflow like modulus 2^32?

I imagine this is somewhat hardware specific, so I’ll take GeForce 8800 as the example platform.

p.s. integer math appears to overflow “gracefully” on GeForce 8800 GTS. That is, the low 32 bits are correct.