[HECnet] Silly RSX questions....

[Bob Armstrong]

I don't know if you understand the concept of memory partitions in RSX
properly.

  No, I guess not.   The usefulness of partitions in an unmapped system is
easy to see - since tasks have to be linked (er, "TKBed") to run at a
specific virtual address and all tasks have to share the same address space
at the same time, you have to fit the tasks into memory.   It's really the
address space that's being partitioned as much as it is the memory.   The
concept is not unlike overlays.

  But once you have an MMU the whole procedure is pointless.   Every task and
every processor mode can have its own contiguous virtual address space.
Nobody needs to share virtual address space with anybody else.   And the
mapping to physical memory is (for practical purposes) completely arbitrary
and easily changed on the fly.   What's gained by partitioning physical
memory into fixed chunks that are allocated only to specific uses and can't
be shared?

  Actually I thought RSX worked the way you described for M+ -> everything
ran in a "GEN" partition, and the system just made as many GEN partitions as
it wanted.   Only if you were unmapped did you care which partition something
ran in.

Good idea. But there are SCSI controllers for the Q-bus, as well as the
KDA50...

  I have both of those, but I'm not going to waste 'em on a 11/23! :-)

  Actually that's a pretty realistic attitude back in the day - these are
more expensive mass storage devices and anybody who could have afforded them
probably would have bought a faster CPU too. 

Bob