[Simh] VAX 11/782 simulation [was: :Re: Pdp8 terminals]

[Jeremy Begg]

Hi,

VMS 5.0 introduced Symmetric MultiProcessing (SMP) and discontinued support for the 782. This would have been in the late 1980s by which time DEC had released "proper" multiprocessor VAX models.

VMS still has the concept of a "primary CPU" and I think there are still some interrupt handlers which run *only* on the primary CPU.

Jeremy Begg

Sent from my iPad

> On 8 Sep 2016, at 4:45 am, Hittner, David T (IS) <david.hittner at ngc.com> wrote:
> 
> Wasn't the VAX 11/782 and the Asymmetric model de-supported at some point during the life of VMS?
> 
> I seem to remember hearing (at a DECUS Symposium?) that existing 11/782 customers would have to separate them into two 11/780's and then cluster them to upgrade to the latest version of VMS.
> 
> Dave
> 
> 
> -----Original Message-----
> From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Johnny Billquist
> Sent: Wednesday, September 07, 2016 2:55 PM
> To: Ray Jewhurst
> Cc: simh at trailing-edge.com
> Subject: EXT :Re: [Simh] Pdp8 terminals
> 
> Hi.
> 
>> On 2016-09-07 19:00, Ray Jewhurst wrote:
>> My apologies. To be honest I am very ignorant about of the science of 
>> computers. I am disabled, cannot work but I am a total computer 
>> history buff. I want to learn and know and experience as much as I can 
>> and Simh is a major part of that. I  want to help where I can so 
>> please excuse my occasionally confusion.
> 
> No worries. You never learn if you are afraid of making mistakes. 
> However, if you are not rather experienced writing code, I think that implementing something like the VAX-11/782 might be quite a task... Not to mention that I don't know where you'd find a version of VMS that would support the machine.
> 
> Maybe find something a little simpler to start with? Like the talk about expanding the PDP-8 to more generic support for devices than the current implementation.
> 
>    Johnny
> 
>> 
>> 
>> On Sep 7, 2016 12:46 PM, "Johnny Billquist" <bqt at softjar.se 
>> <mailto:bqt at softjar.se>> wrote:
>> 
>>    The 11/782 are no more asynchronous than any multiprocessor system.
>> 
>>    The A in ASMP stands for assymetric. As in, the second processor did
>>    not run any kernel code, but is a slave processor to the primary
>>    processor. It gets scheduled with user-land code to run, but any
>>    trapping to the OS means it interrupts the main processor, who do
>>    all the work.
>> 
>>            Johnny
>> 
>>    On 2016-09-07 18:23, Ray Jewhurst wrote:
>> 
>>        I think you are like I am. I would like to see every DEC simulator
>>        possible. Right now I am doing some preliminary research into the
>>        feasibility of a VAX 11/782 which is an asynchronous dual processor
>>        11/780.  I will need help because I am not a real experienced coder.
> 
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