It was never fully developed in the sense that a complete system was built, but it was made into a card that plugged into the back plane of a Sun 3 system. We had one, and our card is shown here:

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Ours is now in the (local) Computer Museum .

Unfortunately most of the software details are lost in the fog of past memories.

However, good information is shown in the page linked in the comments, which indicates that the hardware ran slower than the implementation of the software on the Sun 3, which eventually led to the demise of the project.