G7273 grant continuity card

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G7273 card; front side, showing NPG jumper in upper right corner

The G7273 grant continuity card was dual width card which plugged into the C and D connectors of an SPC slot or MUD slot in a UNIBUS backplane, in an otherwise-empty slot, and carried the bus grant line signals from the 'in' pins to the 'out' pins in the slot.

Unlike the earlier G727 grant continuity card, it carried not only the BG4-BG7 interrupt grant lines, but it also carried the NPG grant line.

In all SPC and MUD backplanes, there was normally a wire-wrap jumper on the rear of the backplane for the NPG line, which had to be removed before a DMA device could be plugged into that slot. The G7273 allowed such a device to be removed, without the necessity of replacing the jumper.

Later PDP-11's, such as the PDP-11/84, made extensive use of the G7273, instead of the G727, so that there was no need to have, or remove, those jumpers.

See also