[Info-vax] CPU Refresher for Programmers

[Johnny Billquist]

On 2016-01-18 22:19, IanD wrote:
> On Monday, January 18, 2016 at 10:48:54 AM UTC+11, Chris Scheers wrote:
>> Conceptually, these "enclaves" look extremely similar to the Data
>> General MV rings of 40 years ago.
>>
>> The only way to call code in a ring is through a defined call gate,
>> outer rings can not access memory in an inner ring, etc.

I never understood the point. So the concept was that, depending on the 
address where your program was executing, you had different privilege 
levels. How was this different from having different modes in the PSL? 
You had to trap through special "gates" to get to a higher level in both 
cases. But one had a weird connection based on address, which in my eyes 
just looked like a stupid limitation and connection that could cause 
funny issues.

> Oh I remember some DG stuff although it was when DG was in decline and Digital was growing and starting to eat their lunch from memory. We used it at an educational institute. I remember only being able to do 6 pascal compiles at a time, which was very painful in a class of 40 students waiting for a compile to get off the queue. We used to run spice circuit analysis on the DG as well. Wow, I had forgotten all about the DG system until mentioned here

DG felt like they were always trying to catch DEC, and never really 
doing it.

>> Among things, I've seen the intermediate rings running networking,
>> databases, and cross process communications.  Anything that requires
>> security from malicious (or just flakey) code is a good candidate.
>>
>> --
>> -----------------------------------------------------------------------
>> Chris Scheers, Applied Synergy, Inc.
>>
>> Voice: 817-237-3360            Internet: chris at applied-synergyxxxx.com
>>     Fax: 817-237-3074
>
> I think the OS was Aviion? Didn't that morph into the OS behind EMC's storage frames?

No, Aviion was a product.
I think Aviion started out as a series of workstations, but I think it 
was also storage, and storage was eventually bought by EMC.
The OS was DG/MV or something like that.

Meh, people can look it up if they want details. Even back in the 80s, I 
didn't particularly care for DG, and I've forgotten most of what I ever 
knew...

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
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