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 W
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 "capabili
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 Pih
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
On Wed, 11 Feb 2015 12:35:28 +
"Shoppa, Tim" wrote:
> Sent from my PDP-8/E
Seriously? That would be mighty impressive!
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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-edg
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,
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
