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

[David Wade]

On 14/01/2019 22:18, Scott Dorsey wrote:
> David Wade  <g4ugm at dave.invalid> wrote:
>>
>> Why does it hang when the card is removed? Thats not expected to me...
>> .. if the CSRs worked before, surely they work the same afterwards....
> 
> There are interrupts which are laddered board-to-board rather than run
> down the backplane.  If there is an empty space in the backplane, the
> cards after the empty space cannot see those interrupts.  Therefore, we
> either move all the other cards up or we put a bus grant card into the
> empty place.
> 
> This allows prioritization, and it is why you put the higher speed
> controllers closer to the CPU in the backplane than you do the slower
> devices.
> --scott
> 

Scott,

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.

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...

Dave