CP6100 I/O Process Programming Manual

Using CP6100: Managing Lines
Some Configuration Issues
Planning a configuration is detailed work. For each kind of line
you decide the values of many parameters, which affect the
electrical interface and protocol operation. The System |
Management Manual for Tandem NonStop Systems describes the |
parameters for each kind of line. This section mentions a few
considerations that apply to all CP6100 lines.
• First, you can use the MULTI parameter to assign as many as
15 lines, possibly running different protocols, to the same
instance of CP6100. The lines must all be attached to the
same 6100 subsystem. This strategy reduces the number of
CP6100 processes that run in the CPU, but increases the
workload of each process. All lines controlled by a single
process are reached by the same path: that is, the CPU,
I/O channel, and controller are the same. If a switch occurs
as a result of an error or an operator request, the switch
applies to all the lines controlled by the process.
• When a system comes up after a cold load, I/O processes don't
necessarily start in the right CPUs for the dual-port |
controller environment. You may have to use CMI (ALTER CIU) |
to impose the desired configuration. Although a CONTROLLERS
or PERIPHERALS entry does not ensure correct CPU assignment,
it should always describe the assignment you intend to use.
For the single-port controller environment, all I/O processes |
start up in the same CPU. You must use CMI to impose the |
desired configuration. |
• When you define the controllers in a subsystem (in the
CONTROLLERS paragraph), you can give them the same or
different primary CPUs. If they have the same CPU, it will
bear most of the processing load for the lines, except in
the case of a CPU switch. Assigning a different CPU to each
controller spreads the processing load. For the single-port |
controller environment, the CONTROLLERS paragraph implies that |
there is only one controller. |
• When you define each line (in the PERIPHERALS paragraph), you
indicate the path used for access to the line. Paths were
defined in the PATHS paragraph; a path name implies a specific
controller and CPU. You can balance the workload in the
subsystem if you assign lines to each path on the basis of
how much traffic you expect on each line and what the overhead
is for controlling it. All lines for which you specify the
same path name must switch CPUs together; on the other hand,
if an error or command forces a controller switch, only those
lines associated with the same I/O process must switch. This |
is not applicable to the single-port controller environment. |
• You can describe lines to SYSGEN before you install them
physically in the system, provided that you set the STARTBOOT
October 1985
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