Not trade secrets, by definition, because all was exposed. In fact, if I remember correctly, IBM even published on paper the assembly for their (first) BIOS.

Not trade secrets, by definition, because all was exposed. In fact, if I remember correctly, IBM even published on paper the assembly for their (first) BIOS. This is a copyright vs. patent sort of thing. What Phoenix copied using the "Chinese Wall" technique is the sort of thing that might be covered by patents, that is, ideas. The IBM BIOS was a creative implementation/expression of those ideas, and that code was copyright protected, as was Phoenix's independent version of the code that implemented the same ideas.