Since there is no released build of Kiwi, there are no fixed requirements, however here is some advice for supported hardware should you wish to use Kiwi.
Kiwi is not designed to run on the ancient computer sitting in your attic. We are focusing on computers that we would expect most users to use in the present. Therefore, the minimum processor family required is a Pentium 3 or equivalent processor. By targeting newer chips (not that the P3 is incredibly modern), we can use modern instructions to make Kiwi more efficient and quicker. Furthermore, if you are running a 32bit version of Kiwi, then your processor must support PAE otherwise Kiwi will not boot.