Booting an IBM MP 3000 S/390 System
cclist at sydex.com
Thu Aug 6 14:29:27 CDT 2015
Another reason for an attached service processor is to handle twiddling
of things that the main machine shouldn't have access to. Reconfiguring
memory, adjusting operating margins, monitoring water temperature,
getting hold of detailed status information, etc. In at least one case,
I'm aware of a machine where the MCU could reconfigure memory so that
the CPU could continue running while the MCU ran diagnostics on the
invisible (to the CPU) memory. Other than somewhat degraded memory
size, the CPU was none the wiser.
Some CDC MCUs employed a drum for its own program as well as for storing
microcode--and had its own (separate) display console.
More information about the cctalk