Another major problem was its immature and untuned Ada compiler. It used high-cost object-oriented instructions in every case, instead of the faster scalar instructions where it would have made sense to do so. For instance the iAPX 432 included a very expensive inter-module procedure call instruction, which the compiler used for all calls, despite the existence of much faster branch and link instructions. Another very slow call was enter_environment, which set up the memory protection. The compiler ran this for every single variable in the system, even when variables were used inside an existing environment and did not have to be checked. To make matters worse, data passed to and from procedures was always passed by value-return rather than by reference. When running the Dhrystone benchmark, parameter passing took ten times longer than all other computations combined.