VAX 4000-100 QBUS cables

Maciej W. Rozycki macro at
Mon Nov 28 11:29:56 CST 2016

On Mon, 28 Nov 2016, Pontus Pihlgren wrote:

> >  FYI, the VAX 4000-100/105/106 (KA52/KA54/KA54) systems have no backplane 
> > of any kind and do not use Q-bus internally, except for the CQBIC (CVAX to 
> > Q22-Bus Interface Chip) ASIC directly bridging one of the NCA (NDAL to 
> > CDAL Adapter, or the north bridge in modern speak) ASIC's CP peripheral 
> > buses to a mainboard Q-bus connector further wired with an internal cable 
> > assembly to the pair of external connectors mounted on the backside of the 
> > enclosure.
> Thanks for clearing it up. Uhm, stupid question perhaps. But what is the 
> CDAL, and what is it's role?

 CDAL aka CVAX Data and Address Line bus is the original CVAX processor 
host bus.

 In the NVAX chipset used with the 4000-100/105/106 systems apart from the 
CPU(s) the NDAL host bus has two other devices only: the NMC ASIC (NVAX 
Memory Controller) and the NCA ASIC (as above; also termed NVAX I/O 
Adapter sometimes).  The NMC bridges two separate CDAL buses, called CP1 
and CP2, which let connect original CVAX peripherals unmodified (so e.g. 
the 4000-60's TURBOchannel adapter which interfaces to CDAL can be used 
unmodified in the 4000-90/90A/96 systems, which use the same NVAX 
chipset).  There's a further bridge downstream on one of the CDAL buses, 
CEAC (CDAL to EDAL Adapter Chip), which interfaces 16-bit peripherals.

 Have a look at VAX 4000-100/105/106 documentation for a block diagram, 
which will serve you better than this textual description.


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