Subject: Re: Dilog 703 SCSI controller question
To: None <>
From: NetBSD Bob <>
List: port-vax
Date: 01/03/2001 15:55:06
> > The only
> > gotcha might be the HD50 connector end for outboard devices.  
> Yes. SCSI uses a female connector, DSSI a male one _AND_ the pinout is
> different. I checked this. DSSI uses a mapping:
> flat ribbon cabele	HD50 plug
> 	1		1
> 	2		2
> 	3		3
> 	4		4
> SCSI uses:
> flat ribbon cabele	HD50 plug
> 	1		1
> 	2		26
> 	3		2
> 	4		27
> 	5		3
> 	6		28

OK, that is the shortcut they took in wrapping the cabling around
between the two sides of the HD50.

The main cabinet cable appears to be straight through, from the
KA640 cpu up to the drive bay wall mounted 50 pin dip receptacle.
Then, the DSSI uses a straight 50 pin flat ribbon cable, but the
end has the DSSI twist where the cable is cut in half at 25/26 wire
and then the cable is folded to make the dssi backside, thus:

    1                       25
    50                      27

It is sort of like I used to do in making 8 inch drive external
cabling for some of my old S100 box crates, years ago.  That way
a couple of DB25 ribbon connectors could split a 50 pin bus, easily.

I can make up another 50 pin ribbon thing, and make it long enough
to follow out and up to an external drive box, if needed.

I could also make up a custom patch cable that would follow the
DSSI routing map except swap back to scsi at the external drive bay.
Crude, but that should cure the mismatching, if done correctly.

The thing I really need to know is if that 50 pin round DSSI cable
running from the drive bay down to the CPU is pin/pin compatible
with a straight scsi 50 pin run.  I THINK it is, but need to make
sure of that.  If that is the case, then I can use that existing
cpu to drive bay cable run as a scsi cable rather than a DSSI

> > Can those harnesses be used as scsi cabling
> > for an SQ706 type of controller in the MV3300 dssi crate?
> I think yes, if you build your own special SCSI terminator for the DSSI
> plug. But it will be much easier to use a separate cable for SCSI. 

OK, I can make up the last internal 20cm cable, but I need to make
sure about that meter long internal drive bay to cpu thingie.



Gee... aren't VAXentoyz fun!

Thought.... while we are on the wierdoVAXenconfiguration thingie...

Can the VS60 cabinet be made to emulate, functionally, a BA215 or
BA123 cabinet?  IF SO, I could use the VS60 cabinet to mount up
4 scsi drives and by changing the backplane to use the MVII or
BA213 style serpentine or straight Qbus backplane, make up a
really fine MVII kind of critter (finding another BA123 cabinet
would probably be the better choice, though).

Just musing out loud in the wierdoVAXentoyz mode.....(:+}}.....