tony duell wrote:
The RH11 do DMA, just like all other disk controllers I
know of.
IIRC, the RX11/RX211 (Unibus) and RXV11/RXV21 (Qbus) don't do DMA.
The RX11/RXV11 don't do DMA, but the RX211 and RXV21 do, I think
I can confirm that the RXV11 for the Qbus does not and I am also fairly
confident that the RX11 for the Unibus does not as well. Under RT-11,
the device driver is the DX(X).SYS device driver and an inspection of
the code confirms the lack of DMA as well.
I can confirm that the RXV21 for the Qbus does and I am also fairly
confident that the RX211 for the Unibus does as well. Under RT-11,
the device driver is the DY(X).SYS device driver and an inspection of
the code confirms the presence of DMA as well.
More in my reply to Jerry Weiss.
Jerome Fine