[Info-vax] clock problems with OpenVMS x86 on VirtualBox

[gah4]

On Saturday, May 6, 2023 at 9:49:43 AM UTC-7, Craig A. Berry wrote:
> I am running OpenVMS x86_64 E9.2-1 under VirtualBox 7.0.8 on macOS 
> Ventura 13.3.1 (a). The host is a 2019 MacBook Pro with 2.3 GHz 8-Core 
> Intel Core i9. The clock isn't working right, most easily seen by the 
> fact that the following two commands were typed exactly one minute apart: 
 
> $ sh time 
> 5-MAY-2023 19:07:35 
> $ sh time 
> 5-MAY-2023 19:07:45 
 
I haven't thought about this recently.

As well as I know it, many OS were designed to know about emulators, 
and virtual machines, and virtual machines to know about client systems.

The OS should be able to request the right time from VirtualBox.

IBM used to develop new OS running under VM/CMS, so they had to
figure out that early.  I suspect it is not unusual to develop OS now
using virtualization.  

It might be, though, that someone hasn't gotten around to that one.

Note that IBM S/360 and successors have a convenience for emulation.
OS enter a wait state, when there isn't anything else to do. They stop executing
instructions, and so there is no idle process.

That goes back to the days when hardware was rented, and rental depended
on how much it was used.  That is, it would stop charging when the system
stopped executing instructions. 

Many emulators and hypervisors recognize the idle loop, though.

How does VMS keep track of time?