Many years ago, I designed the TURBOchannel adapter for the VAXstations 4000/60, /90, and /96. Among the things I delivered to DEC was a manual for the thing, which was used by them to write the official manual and develop diagnostics.
Although I've never seen the official DEC documentation, I have recently stumbled across the manual that I delivered.
You can find it here. The table of contents is here.