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

[Arne Vajhøj]

On 5/13/2023 3:30 AM, Fred. Zwarts wrote:
> Op 13.mei.2023 om 02:18 schreef Arne Vajhøj:
>> On 5/12/2023 8:41 AM, bill wrote:
>>> On 5/12/2023 8:14 AM, Simon Clubley wrote:
>>>> On 2023-05-12, Jan-Erik Söderholm <jan-erik.soderholm at telia.com> wrote:
>>>>> Actually, that was how I thought it worked. Since I observed that
>>>>> the clock in my VirtualBox VMS environment lagge a bit behind
>>>>> but each 10-20 sec, it jumpt ahead and skipped a second so that
>>>>> it become in sync with the host Windows environment again.
>>>>
>>>> That's going to make for some "interesting" real-time program 
>>>> behaviour... :-)
>>>
>>> Does VMS still claim to be an RTOS?  Did it ever (there was VAXELN)?
>>
>> I don't think it ever has.
>>
>> But 30 years ago most believed that VMS had better
>> real time characteristics than Unix.
> 
> In 1980 the RT properties of VMS were part of the decision to by a VAX 
> for our nuclear physics laboratory, i.e. the special scheduling of 'Real 
> Time' priority processes.
> I don't know if those properties are still present.

VAX got real time priorities 16-31.

Alpha got real time priorities 16-63.

I assume Itanium and x86-64 has 16-63 as well.

But I believe there is more to real time than
having those (no quantum end and no dynamic
adjustment).

Arne