PDP-11 Memory

[Noel Chiappa]

    > From: Allison Parent

    > Most Probable cause is interrupt grant is broken.

The only -11 that complains if the grant chain is broken that I know of is
the /34 (maybe the /04 too). I certainly have a QBUS chassis right next to my
workstation here that i) has a bunch of empty slots, and ii) works fine, as
long as there are no empty slots between the CPU and the devices.

Also, IIRC he said it works with 3 cards plugged in, but not 4; how can
plugging a card _in_ cause grant problems?

    > For most microspheres backplanes the first three slots are different
    > than remaining.

That might be worth checking into. I'm not familiar with the second box
he's using, so can't help there.

	Noel