[Info-vax] Alternative _legal_ operating systems for VAX ?

[Johnny Billquist]

On 2022-01-02 22:01, Arne Vajhøj wrote:
> On 1/2/2022 1:36 PM, Johnny Billquist wrote:
>> On 2022-01-02 16:11, Arne Vajhøj wrote:
>>> On 1/2/2022 3:39 AM, Simon Clubley wrote:
>>>> Before deleting my simh instances, I thought I would look for
>>>> other operating systems which ran on VAX and try them out.
>>>>
>>>> The only current one I have found is NetBSD (which certainly has
>>>> a _very_ retro 1980s Unix feel to it. :-)).
>>>>
>>>> OpenBSD dropped VAX as an architecture a number of years ago.
>>>>
>>>> Does anyone know of any other operating systems (including any
>>>> experimental ones) for VAX that are still legal to run under simh ?
>>>>
>>>> If so, do you have any links to them ?
>>>
>>> Wikipedia lists BSD 4.3, NetBSD, OpenBSD and something called Xinu
>>> as open source options for VAX.
>>
>> As far as I know Mt. Xinu (read it backwards? ;-) ) wasn't free. I ran 
>> it on an 8650 for a while. I think I still know where the manuals are, 
>> but I'm unsure if I know where the tapes are...
> 
> https://www.cs.purdue.edu/homes/dec/xlicense.html

My bad. Xinu and Mt. Xinu are apparently two different things. Sorry for 
the noise.

>>> NetBSD may be the only one with current support. But do you need to run
>>> a current version??
>>>
>>> You did not run a current VMS version on it.
>>>
>>> And resource wise it may be a better fit for an older OS
>>> anyway.
>>
>> That is definitely true. It's not that pleasant to run current NetBSD 
>> on any VAX at the moment. But there are also some problems/issues that 
>> we're waiting for a new version of gcc to come along, where they have 
>> been fixed.
>>
>>> Alternatively you could take up the Linux VAX port. Some
>>> work was done many years ago and I believe they got pretty
>>> far.
>>
>> I think it booted to single user mode. Not sure it got much further. 
>> Not sure anyone would even want to try and pick that up, as Linux is 
>> constantly changing under the hood, making it a big task to resume 
>> something abandoned years ago.
> 
> Remember that Simon believes using C makes porting easy.
> 
> Great opportunity to demonstrate.
> 
> :-)

Well, this has close to nothing to do with C.
If the API is changed, it's a headache.
And porting operating systems requires a lot of code to deal with the 
specifics of the hardware, which is inherently not that portable.

And thus - if you have code that deals with the hardware, but which is 
using an API that no longer exists, you need to either rewrite all the 
code that deals with the hardware, or rewrite all the code that makes 
use of the API to the rest of the OS, which might also force changes in 
code that deals with the hardware.

Makes no difference which language you are working in, and no matter how 
easy a language would be for porting, the problem here don't change.

All that said, I actually do believe that C is easier to port than 
Macro-32. :-)

   Johnny