> I have some questions since I'm working on an R2R NuBUS sound adaptor.

Cool!

> 1.  Does each slot have its own data bus (are they all connected together
>     or not?)
> 2.  Does each slot have its own address bus (are they shared except the
>     upper bit?)

I believe they are all connected together, although each card is
assigned a specific address range and they may not actually drive
the bus if they access within their own range.

> 3.  Which bits on the NuBUS address bus set the current card?

There are two memory ranges for each card: "normal" and "super".
"Normal" space is masked by 0x0SFFFFFF where the 'S' is the slot # (9-E).
"Super" space is masked by 0xSFFFFFFF.  If you pick up a copy of
Designing Cards and Drivers for the Macintosh, 2nd edition or maybe
the third (I have the second) it explains some of this in excruciating
detail.  The Slot Manager docs at
http://developer.apple.com/techpubs/hardware/DeviceManagers/slotmgr/slotmgr.html
might help some, too.

> 4.  Does each card have its own /RD / /WR wires, or are they shared with
> all the cards?

No clue how this is handled...

Nubus is IEEE 1196, though, if you have access to a library with IEEE
standards.

Have fun!

-allen