@mcc sounds like an expensive exercise in planned obsolescence. System capacities keep growing, and just like 32bit RAM sizes eventually grew to fill the entire 32bit address space, the same will happen to 64bit. And your fallback code has to match 100% of the desired functionality, and be tested as extensively, and in the long run is going to have a longer operational life with greater platform compat than the bit-stealing code. Easier to just do the work once, and move on.