[Simh] A terminology question

[Pontus Pihlgren]

If I understand it correctly, you have four combinations:

11 -- illegal
10 -- data
01 -- instruction
00 -- illegal

And memory locations market illegal or data wont be executed?

This reminds me of the more modern terms "DEP" - Data Execution 
Prevention, "NX" - No-eXecute, "XD" - eXecute Disable, "XN" - eXecute 
Never. DEP and NX seems to be a generic terms and the others are 
platform specific. Different OSs that take advantage of this calls it 
different things.

Not quite the same as the DEP is usually enforced on memory pages.

/P

On Mon, Feb 09, 2015 at 12:32:47PM -0800, Leo Broukhis wrote:
> Dear colleagues,
> 
> There is an implementation detail in the BESM-6 architecture the name of
> which we've struggled to translate adequately.  There is a feature
> preventing execution of arbitrary data as instructions implemented using
> two parity bits per word, for the upper and the lower half-word. The
> overall parity must be odd, and one of the valid parity bit configurations
> denotes an instruction, and the other denotes data. In the original
> documentation this mechanism was called
> https://translate.google.com/#ru/en/%D1%81%D0%B2%D0%B5%D1%80%D1%82%D0%BA%D0%B0
> (the two forms were called literally "command convolution" and "number
> convolution").
> 
> Unlike a tagged architecture, there isn't a fixed tag value to indicate
> instructions or data.
> 
> Is there a standard term for this? "Convolution" sounds too mathematical.
> 
> Thanks,
> Leo

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