Use of DMA Ring Boards

Ring DMA boards will be put in the following machines:-

      Nodes         2
      Fep's         2
      Pss Gateway   1
      X25 Gateway   1
      ERTE          1
      Dev. Machine  1
      Filestore     2

Four of these connections are new, ie the filestore machines, the second
FEP, and the 11/60 (or more correctly giving ERTE back its ring interface).

In addition, when the single word boards are released, TCP D will be
moved onto the ring as part of the switch to X25.