[comp.arch] VME bus broadcasting?

jim_d@cimcor.mn.org (Jim Dahlberg) (02/14/89)

    I am working on a multiprocessor system which will have
multiprocessors on the VME bus.  It will be necessary for the
application software to broadcast data to the other processors' local
memory.  Does anybody know if this has been done, or if it is feasable?
    If necessary, we can 'bend' the VME spec to allow this, since we
are already planning to use a non-standard VME connector.  Also all the
VME cards will be unique, so they don't have to conform to the standard.
But we would like to stay with the standard as much as possible.

    Jim Dahlberg
    Internet: jim_d@cimcor.mn.org
    UUCP:     uunet!rosevax!cimcor!jim_d
    UUCP:     orbit!pnet!jad

markw@hpsal2.HP.COM (Mark Williams) (02/16/89)

|  I am working on a multiprocessor system on the VME bus.  [How can I]
|  broadcast data to the other processors' local memory?

Try the following:

Dedicate some region of VME address space or a "User defined" address
modifier code (10-1F) to the broadcast address space.  To do a broadcast,
issue a write to the broadcast space.  Your VME processors will
accept the broadcast and no others will be affected.

Depending on what you want to use broadcasts for, you may want to
self-acknowledge (assert DTACK) the VME broadcast at the master
(if, for example, the broadcast is a reset, which must be reliable).