VAX Q-bus identical to PDP-11 Q-bus?

Jon Elson elson at
Thu Dec 7 10:50:21 CST 2017

On 12/06/2017 03:43 PM, Aaron Jackson via cctalk wrote:
> Thanks Glen and Jerry.
> I think that settled that debate! haha
> Thanks,
> Aaron.
> Glen Slick writes:
>> An M5976 KZQSA is not MSCP compatible so it wouldn't do any good with a
>> PDP-11 system. It's really only useful for RRD4x SCSI CD-ROM drives with
>> VMS on a VAX 4000.
MSCP is a software protocol.  Any device that has a driver 
available for the PDP-11 operating system you want to use 
can use that device.  Most of the really old disk and tape 
interfaces were NOT MSCP compatible.  We also hacked up some 
oddball drivers to use old PDP-11-type devices on VAXes.

But, yes, if there's no driver to support the interface, 
then it doesn't really matter if the device is electrically 


More information about the cctalk mailing list