P.D.Helliwell <P.D.Helliwell@e-eng.hull.ac.uk> wrote:
> OK, here's the snag.  It's in a BA123 case, but we only have the manual 
> for the MVII in the BA23 case.  Are there any recommended places for 
> specific cards on the Q bus ?  In the manual it recommends putting the 
> RQDX3 in Q bus slot 13.  This seems a but unlikely for the BA123 as 13 is 
> outside the (box with the fan inside thing ..).

Slot 13 is not really a Q22-bus slot. It doesn't provide any Q22-bus signals,
only power and ground. RQDXn doesn't connect to the drives directly, but does
so through a so-called signal distribution board. The RQDX3 goes into a Q22-bus
slot. The signal distribution board goes into a slot that provides only ground
and power. In a BA123 that is either the upper or the lower half of slot 13.
The RQDX3 connects to the signal distribution board with a straight
50-conductor ribbon cable. The signal distribution board has a pair of header
connectors (one 34-lead and one 20-lead) for each of the 4 Winchester disk
drives (WDDs) and one 34-lead connector for the floppy disk drive (FDD). All of
these connect to the respective drives with straight ribbon cables. This is a
radial configuration, not a daisy-chain one. All drives should have their
terminator packs installed. The unit select jumpers on the WDDs can be set to
anything, since the unit number is determined by the position of the cables on
the signal distribution board, not by the jumpers. (The board asserts all 4
unit select signals on one connector but not on any others.) The FDD is more
tricky. RX50, AFAIK, doesn't have any jumpers on it, but if you want to connect
an RX33 (either a real one or a standard 5.25" "high-density" FDD), you'll
probably need to set the unit select jumper to something particular. For the
MFM controller on KA410 (a BabyVAX system board) it's unit 0, but this
controller is different enough from RQDX3 (doesn't use a signal distribution
board, etc.) to make it far from obvious that what applies to it should also
apply to RQDX3. (The two use the same base chip, SMC HDC9224, though, so the
WDDs can be moved between them. This is good since Winchester disk formatting
is so much easier on a KA410 compared to an RQDX3. This is also why you can
connect an RX33 to an RQDX3 while RQDX1/2 support only RX50.) You also need to
set some jumpers, either on the RQDX3 itself or on the signal distribution
board, to tell it whom should it wake up when unit 2 or 3 is selected: WDD 2/3
or the FDD. Unfortunately, my docs are unclear on this. Also if you are
constructing an RX33 from a standard 5.25" "high-density" FDD, you must set it
to the dual-speed mode. Unfortunately, since most companies nowadays make
PeeCee-only shit, a lot of FDDs don't have this capability.

> When we try to boot to the RX50 disk sets from the monitor prompt, 
> whatever we try we got "device inactive".  The two addresses on the cards 
> are different, well as far as the manual says they're different.  Am I 
> right in thinking that it treats RX50s as disks so we could boot with 
> something like
> 
> >>> b/3 DUA0
> 
> (controller A, disk 0) ?

Yes, except that it's unit 2 or 3, not 0. RX50 is a "dual-deck" drive. One of
its "decks" is unit 2 and the other is unit 3.

Sincerely,
Michael Sokolov
Phone: 440-449-0299
ARPA Internet SMTP mail: sokolov@alpha.ces.cwru.edu