Please consider adding SPMODE to the default cm370ce configuration #142
Description
re: Bob Polmanter's SPMODE Single Processor Mode for VM/370 (https://groups.io/g/h390-vm/message/6594)
SPMODE allows VM/370 to run on a single CP of a multi CP system. this allows guest OSes like MVS to run on a dedicated processor and dedicated I/O outside of VM's interaction. This allows MVS as a guest under VM to run significantly faster, nearly on par with MVS running directly on Hercules. ("nearly" on par).
This would require installing Bob's SPMODE changes to the VM nucleus and rebuilding it, adding a 2nd CPU to Hercules' config, and adding a command to AUTOLOG1's PROFILE EXEC to enable SPMODE at IPL time to make it automatic.
Without running anything as a guest on the 2nd CPU, VM running on a single CP in SPMODE doesn't seem to act any differently than VM/370 running on a single CP machine as far as I'm able to tell, so adding this to vm370ce should be a no-op as far as non-MVS users are concerned, performance-wise and operationally. However it would add a huge benefit to users running some flavor of MVS or other large guest OS on the system.
The code and Bob's awesomely detailed installation instructions are at https://groups.io/g/h390-vm/files/spmodev101.zip
I've been running this now a week or two without any noticeable differences in operation.