Re: Regarding interrupt sharing architectures!

Jim Stewart wrote:
Paul Keinanen wrote:

On PDP-11's the "bus grant" card was inserted into empty card slots to
get interrupt continuity.

Unfortunately these "continuity" cards were very small, installing one
into a slot previously occupied by an other card would either cause a
few bleeding fingers :-) or you had to remove the neighbouring cards,
insert the small bus grant card and then reinstall the original cards.

Just a minor detail, if the bus grant card had been of full size,
there would not have been any problems installing or removing it when
actual cards were removed or installed.

Field service calls were not unusual after
a customer "reconfigured" their machine and
didn't get the bus grant card right.

I spent my early 20's maintaining DEC and
DG minis.  I have a working pdp 8/l in the

There was a similar daisy-chain of interrupt and DMA chains in the DG minis.


Tauno Voipio
tauno voipio (at) iki fi