MC_SERVICES_P6

   (Alpha only) MC_SERVICES_P6 specifies MEMORY CHANNEL message
   size, the body of an entry in a free queue, or a work queue. The
   maximum value is 65536, and the minimum value is 544.

   The default value is 992. This value is suitable in all cases
   except for systems with highly constrained memory. For such
   systems, you can reduce the memory consumptions of MEMORY CHANNEL
   by slightly reducing the default value of 992. The value of MC_
   SERVICES_P6 must always be equal to or greater than the result of
   the following calculations:

   1. Select the larger of SCS_MAXMSG and SCS_MAXDG.

   2. Round that value up to the next quadword.

   The value of MC_SERVICES_P6 must be the same on all nodes
   connected by MEMORY CHANNEL.