[Info-vax] OT: obscure PDP11 OSes (even more dinosaury)

[Johnny Billquist]

On 2015-06-22 17:32, Jan-Erik Soderholm wrote:
> David Froble skrev den 2015-06-22 17:29:
>> Johnny Billquist wrote:
>>> On 2015-06-15 15:36, Simon Clubley wrote:
>>>> On 2015-06-15, Dirk Munk <munk at home.nl> wrote:
>>>>> bill at server3.cs.uofs.edu (Bill Gunshannon) wrote:
>>>>>>
>>>>>> Of course, all of this still doesn't explain how the VAX was
>>>>>> "a best-seller" when compared to the PDP-11 when the PDP-11
>>>>>> sold 50% more systems.
>>>>>>
>>>>>
>>>>> Because one VAX could do the work of several PDP-11's?
>>>>
>>>> In the early days of the VAX, wasn't there some literature floating
>>>> around showing how the PDP-11 was faster at some things than the VAX ?
>>>>
>>>> This was before my time however so I may be wrongly remembering
>>>> something I read in the past.
>>>
>>> Interrupt response times on the PDP-11 are way better than on VAXen,
>>> which led to people not wanting to downgrade from a PDP-11 to a VAX...
>>>
>>>     Johnny
>>>
>>
>> Swapping can be rather detrimental to observed interrupt times ....
>>
>> When your program is sitting in memory, because it can, things are
>> usually
>> better.
>>
>> Ok, I'm not saying there weren't some things the PDP-11 did better,
>> when it
>> wasn't over burdened with more tasks than the memory could handle.
>
> Many former PDP-11 applications (where "real-time" and interrupt respons
> time matters) have probably been replaced with PLC based or similar
> "embedded" solutions.

Today that is definitely true. There are still PDP-11s out there, but 
fewer than in the past. But then again, that is also true for VAXen - 
even more so than for PDP-11s, I think.

> The VMS system can then talk directly to the PLCs (or other boxes)
> instead...

Right.

	Johnny