Sorry, I have to disagree with some of what was written:

>  Then again, the RQDX1/RQDX2 didn't pass grants properly so
> unless I understand wrong you couldn't have >1 in a system anyway, maybe
> by the time the RQDX3 came along they figured it wasn't worth losing too
> much sleep over (since it's a stupid rule anyway) so they didn't "fix" it.
> ...
> All controllers and units must support unit numbers in the range 0 through
> 251 (inclusive);  ....
> 
> Sounds like the RQDX1/2/3 blew it!


And Dave McGuire wrote

>   There is another set of jumpers on the RQDXx controllers that
> determine the unit number offset, if I recall correctly.

Absolutely.

I'm least certain about the RQDX1 (don't have one), somewhat certain
about the RQDX2 (don't use it much), and I'm sure about the RQDX3 (a
whopping 2 of 'em!). I know I've had the 2 & 3 in the uVax at the same
time, and the drive on the RQDX3 worked (it being last on the bus).
I've also had Both RQDX3's in, no problem there either.  So much for
grants not working on those two, they work for me!

Sorry, I know this is all pretty much documented but...

Each RQDX3 supports 4 drives, at units 0-3 (2 hard drives and an RD50
makes 4. I've never gotten 3 or 4 on one). I don't have the docs on
hand about the RQDX{1,2}, so I can't comment on their abilities.

To get drive 4-7 configured on the RQDX3, you set a jumper on the next
card. You could probably jumper it as drives 248-251 and it probably
would find the drives just fine. The drives themselves in this setup
get units 0-3 again, since after all that's all they can do and the
card make up the offset factor. I've done it to get unit 4 going.

Maybe someone has any info on the RQDX1, and (what I would think
more useful to most) any comments on what might be different about the
RQDX2 from what I've described of the RQDX3. 

Zach