This must be it then: do { z = (x & 0xffff) y + (xc >> 16) + carry; carry = z >> 16; Storeinc(xc, z, z2); z2 = (x++ >> 16) * y + (*xc & 0xffff) + carry;

This must be it then: do { z = (x & 0xffff) y + (xc >> 16) + carry; carry = z >> 16; Storeinc(xc, z, z2); z2 = (x++ >> 16) * y + (*xc & 0xffff) + carry; carry = z2 >> 16; } while(x < xae); Hit up gdb and watch xae and x... I'll try myself but I don't have 32bit.