[Simh] Throttling and this release

[Stephen Hoffman]

Circa Sat, 7 Jul 2012 15:00:38 -0700, Mark Pizzolato - Info Comm <Mark at infocomm.com> posited:
> This is exactly the goal.  
> IPL 1 is not used anywhere in the NetBSD kernel so this the transition to IPL 1 can be used as the idle trigger for that OS.

Solely as VAX trivia and not as a solution for NetBSD or OpenVMS VAX, VAX had an architected idle notification mechanism for operating in a virtual machine, and related instructions and registers.

02FD  WAIT  Wait for Interrupt

This instruction signals idle time from the guest operating system to the real machine operating system (RMOS); from the guest to the virtual machine.

OpenVMS VAX does not implement WAIT nor other related instructions, which means that this is architectural trivia and not generally useful for idle detection nor related virtual machine processing.

For details, see chapter 12 of DEC Standard 32 <http://bitsavers.org/pdf/dec/vax/archSpec/> document.  Don't bother looking in your handbook.

Yes; using IPL detection is the easiest approach, and generally applicable.