Unfortunately, the article didn't address the #1 question on my mind. How closely interconnected were the Genesis and PC sides, did they share a bus?

A little searching and I found this forum thread where some Genesis hackers who have Teradrives assembled detailed info including high-res mobo photos as well as chip pinouts.

http://gendev.spritesmind.net/forum/viewtopic.php?f=2&t=...