> 
> I found that there is this BI-to-UNIBUS adapter and I'm 
> wondering if this makes sense to have since UNIBUS devices
> seem like more easy to get than BI devices. But once I have
> that adapter, I guess I'd need a UNIBUS backplane together
> with soome mount/cabinet and power supply (perhaps an
> old 11/780 cabinet?). This sounds like it would get rather 
> involved. Has anyone done this?
> 
Well, Bi-bus cards are normally not difficult to get. The BI-Unibus
adapter was more commonly used on 8200's, the 6000 machines mostly used
only BI (and XMI) cards.

> The other thing that I'm wondering is the BI busses in the
> VAX 6000-400 are undersized. Why did they even put 2 
> BI backplanes in if a BI bus could logically support 14
> cards? Now the two BI busses together can just about 
> serve 10 cards. Isn't this a waste? 
> 
See it from the other point: the BI bus can handle a maximum of 13.3MB/s,
so if you need to shuffle more data you need more buses :-)
The 8800 we have here has four BI buses to keep up with the I/O speed.
(Parenthesis: The Unibus peeks at 1.5MB and Qbus 3.3MB).

-- Ragge