Truth of the matter, at the time of the 133A chipsets (and nice chipsets that they are -- I'm running a Tyan Trinity 400 here.) the AGP 4x was more wishful thinking than an actual feature.
Few cards at that time were actually supported by the 4x. If you really need the 4x, you're best solution is to upgrade to system components which are more capable of actually accomplishing this task.
I'm not being critical here, just stating the facts.
Hardware has come a long way since the day of the 133A. There are good reasons for that.
I long for the day when I can afford a more modern system.
The reason a diamond shines so brightly is because it has many facets which reflect light.