[Info-vax] DZQ11 on VAX/4000 Model 300

[Stephen Hoffman]

On 2019-01-14 22:41:35 +0000, David Wade said:

> That I understood. The board I added was a 4-port serial which I 
> understood to be low priority. Therefore I placed it at the left hand 
> side of the existing cards. It all worked.
> 
> When I removed it it was the last card on the BUS so there were no gaps.

The daisy chain—the DMA grant and related—is part of the mess here.  
The CSR and vector addresses can and variously do change when the Q-Bus 
bus is reconfigured.

> Given the limited config, as far as I can see the default settings for 
> each card should be fine. However I will re-run CONFIGURE and see what 
> it suggests for board configurations...

Some of these old beasts had a load board as the power supplies needed 
enough of a power draw and an empty half-box was enough to fault out 
the supplies, not that I've looked at a BA box in a very long while, 
and not that I recall whether the BA440 was one of the backplanes that 
required a load board when it was mostly-empty.   One obvious 
work-around was to use a few grant cards and to move some random Q-Bus 
board over into the other half of the backplane, if there wasn't a load 
board handy.

But CONFIGURE is your friend, any time you make any changes to the Q-bus.

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