> I recall a long time ago reading something about potential uses of a 128-bit CPU architecture with 128-bit addressing. Go back to the IBM System/38 and the A

> I recall a long time ago reading something about potential uses of a 128-bit CPU architecture with 128-bit addressing. Go back to the IBM System/38 and the AS/400 and that is exactly what you have. Programs are actually 128 bit oriented bytecode, so the actual CPU architecture isn't visible, doesn't matter, and has been upgraded many times over the years. They also did virtual memory differently. Everything is in the same address space, which means everything can (after access control) communicate and cooperate. Task switches are also very fast. They also use tagged pointers, but it is a single bit outside of what the apps can see, and marks a pointer as modified. Consequently pointers can be given out, and the kernel knowns if the app has tampered with them. I highly recommend reading the architects book about how all this stuff worked, mixed in with how business machines should behave. Many things are very different than conventional Unix/Linux/Windows NT kernels, and a good way of broadening your mind. The second edition book is good - later editions may have removed earlier interesting detail. http://www.amazon.com/Inside-AS-400-Second-Edition/dp/1882419669 http://www.amazon.com/Inside-AS-400-Second-Edition/dp/188241...