I don't know how any 36-bit machine implemented C's char pointers, and I can imagine all kinds of other grief stemming from the ones'-complement arithmetic on the 36-bitters with which I'm familiar, but I can tell you how we implemented char pointers on the 64-bit word-addressable Cray-1, -2, and their descendants. The 3-bit byte offset (big-endian, arbitrarily) of a linear byte address was kept in the most significant bits of a 64-bit word, and the 24-bit or 32-bit regular word address was in the least-significant bits. To do pointer arithmetic, code would have to do circular shifts (more accurately, a shift with fill from the same register) to get a linear address and to put it back into the canonical form that I described.

I don't recall whether a cast to int was raw or converted to linear.