Re: [Simh] A terminology question
In this case the value is calculated from the other bits:
parity({upper half-word, parity bit 1}) = 0, parity({lower half-word,
parity bit 2}) = 1 indicates an instruction word
parity({upper half-word, parity bit 1}) = 1, parity({lower half-word,
parity bit 2}) = 0 indicates a data word
Leo
On Wed, Feb 11, 2015 at 10:48 AM, Phil Budne wrote:
> Leo wrote:
> > "Parity" makes the most sense. I was wondering if there is already a more
> > specific term for such a scheme.
>
> To me, parity implies value calculated from the other bits.
> "tag" or "attribute" bits ring better in my ears. If the tag bits
> can't be tweaked by user code, the term "capability" might be a
> choice.
>
> Phil
>
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Re: [Simh] A terminology question
Leo wrote: > "Parity" makes the most sense. I was wondering if there is already a more > specific term for such a scheme. To me, parity implies value calculated from the other bits. "tag" or "attribute" bits ring better in my ears. If the tag bits can't be tweaked by user code, the term "capability" might be a choice. Phil ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] A terminology question
That's right. An attempt to execute a word with anything but "command
convolution" results in an exception. There were system calls ("extracodes"
in BESM-6 parlance) to store individual words as instructions and to switch
store mode back and forth.
Leo
On Wed, Feb 11, 2015 at 12:23 AM, Pontus Pihlgren
wrote:
> 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
>
> > ___
> > Simh mailing list
> > Simh@trailing-edge.com
> > http://mailman.trailing-edge.com/mailman/listinfo/simh
>
>
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Re: [Simh] A terminology question
Hi Tim, "Parity" makes the most sense. I was wondering if there is already a more specific term for such a scheme. Thanks, Leo On Wed, Feb 11, 2015 at 4:35 AM, Shoppa, Tim wrote: > Rather than "convolution", maybe "parity", "check", "hash", or > "fingerprint"? Like "command parity" and"number parity" plus two "invalid > parities"? > > Many buses have multiple parity bits already (e.g. "address parity" and > "instruction parity" or "upper parity" and "lower parity"). > > Tim. > > Sent from my PDP-8/E > -- > From: Leo Broukhis > Sent: 2/9/2015 3:33 PM > To: simh@trailing-edge.com > Subject: [Simh] A terminology question > > 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 > > ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] A terminology question [off topic]
On Wed, 11 Feb 2015 12:35:28 + "Shoppa, Tim" wrote: > Sent from my PDP-8/E Seriously? That would be mighty impressive! ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] A terminology question
Rather than "convolution", maybe "parity", "check", "hash", or "fingerprint"? Like "command parity" and"number parity" plus two "invalid parities"? Many buses have multiple parity bits already (e.g. "address parity" and "instruction parity" or "upper parity" and "lower parity"). Tim. Sent from my PDP-8/E From: Leo Broukhis<mailto:l...@mailcom.com> Sent: 2/9/2015 3:33 PM To: simh@trailing-edge.com<mailto:simh@trailing-edge.com> Subject: [Simh] A terminology question 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 ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] A terminology question
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 > ___ > Simh mailing list > Simh@trailing-edge.com > http://mailman.trailing-edge.com/mailman/listinfo/simh ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
[Simh] A terminology question
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 ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
