The "Use Fast Input for Input Registers" option is disabled by default in "Optimize Speed" mode. This was enabled by default before 6.2i Service Pack 2.
The fast input register setup time requirements are larger than the single product term path; as a result, this is renamed "direct input" instead of "fast input" in future software revisions and data sheets.
This change is effective in the latest 6.2i Service Pack available at:
The first service pack containing the fix is 6.2i Service Pack 2.