Non-Processor Request and Grant
From Computer History Wiki
Revision as of 16:16, 17 November 2021 by Jnc (talk | contribs) (Jnc moved page Non-Processor Request to Non-Processor Request and Grant: Cover NPG too)
A Non-Processor Request is one of the two kinds of bus requests on the UNIBUS and QBUS; it is used exclusively to gain control of the UNIBUS's data section so that the device may perform a DMA cycle.
The name comes from the fact that the device cannot request that the CPU perform any action (i.e. an interrupt) while the device has control of the bus.
A device gaining control of the UNIBUS via an NPR request may perform more than one master-slave cycle before relinquishing control of the bus, however.
