Hello Michael!

  MT> I have done some experimentation with this.  You can
    > easily do things like use a 3/60 running x-kernel as
    > an intelligent graphics subsystem in the same chassis
    > as a server.

That's a nice idea, off-loading some of the work onto the
3/60 board without needing a separate case.

  MT> To share a backplane between two VMEbus "systems" you
    > can also build a kernel for one "system" that does not
    > have any VMEbus devices. One system can use the left
    > side of a 12 slot chassis and another system can use
    > slots 10-12. The secondary CPU has to have the VMEbus
    > clock generator jumpered off and has to have the
    > VMEbus arbiter jumpered for slave mode. You have to
    > bring both "systems" up in the EPROM monitor before
    > you boot the OS because the monitor probes the VMEbus.

Very interesting in principle, and answers one of the
questions that occurred to me.  In practice I'm probably
going to leave it to those more experienced with SUN's VME
machines, at least for a while! :-)

  MT> Communicating between the boards using TCP/IP is a
    > standard called BusNet.

Excellent, thanks for the link!

  MT> Sun sold software called ONC that supported multiple
    > 1E 6U SPARC CPUs in the same chassis. The CPU number
    > was programmed into the EEPROM. There is a monitor
    > command to boot a secondary CPU from the primary CPU
    > across the VMEbus using ONC.

I'm sure that's got interesting possibilities, and a 6U
case may be easier to come by.

Regards,
  - Andy.