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SMD1990
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More specifically, this question is oriented towards the Intel 8086.
I have this manual that lists the number of clock cycles the 8086 requires to execute each of its instructions, prefixes, et cetera.
My question is about repeat string instructions. The REP prefix is listed as 2 clocks. MOVSx by itself is 18 clocks. REP MOVSx is 9 + (17 / number of repetitions).
If I wanted to count the number of clock cycles the 8086 would consume executing a REP MOVSx instruction in an instance of my code, would I include the REP prefix's 2 clocks for each repetition? Or, do I count it once, then add 9 + (17 / number of repetitions)? Or, does that 9 include the REP, meaning I should not count the prefix as consuming any clock cycles at all?
And what if I used a segment override with the REP MOVSx? Normally, I add 2 clocks for segment override. So +2 for each repetition? Just the first repetition?
Sorry. I know this is a very esoteric question. "Who cares about the 8086?" Right? I do, and I am curious about this unclear situation. So, if anyone happens to know, could they please enlighten me?
http://matthieu.benoit.free.fr/cross/data_sheets/8086_family_Users_Manual.pdf
I have this manual that lists the number of clock cycles the 8086 requires to execute each of its instructions, prefixes, et cetera.
My question is about repeat string instructions. The REP prefix is listed as 2 clocks. MOVSx by itself is 18 clocks. REP MOVSx is 9 + (17 / number of repetitions).
If I wanted to count the number of clock cycles the 8086 would consume executing a REP MOVSx instruction in an instance of my code, would I include the REP prefix's 2 clocks for each repetition? Or, do I count it once, then add 9 + (17 / number of repetitions)? Or, does that 9 include the REP, meaning I should not count the prefix as consuming any clock cycles at all?
And what if I used a segment override with the REP MOVSx? Normally, I add 2 clocks for segment override. So +2 for each repetition? Just the first repetition?
Sorry. I know this is a very esoteric question. "Who cares about the 8086?" Right? I do, and I am curious about this unclear situation. So, if anyone happens to know, could they please enlighten me?
http://matthieu.benoit.free.fr/cross/data_sheets/8086_family_Users_Manual.pdf