General Question about UNIBUS backplanes

william degnan billdegnan at
Sun May 22 13:19:34 CDT 2016

On May 22, 2016 1:22 PM, "Mark Darvill" <mark.darvill at> wrote:
> The core memory/CPU backplane is a special case and doesn’t need grant
> If you have linked up to the expansion Unibus then you need to check you
have the NPG jumper in row C, Pins A1 and B1 in each slot. If these do not
have wire wrap then you will either need to wire wrap them or insert a G727
into the backplane slot. Without these the units will hang on attempting to
use a card that requires DMA access.
> Hope this helps.
> Mark

Thanks Mark..yes I have one slot that needs the npg, it's in place.

I have not had a chance to test with grant cards removed hope that does the

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