> On 2/24/2017 12:22 PM, Don Y wrote:
>> On 2/24/2017 6:52 AM, arshadnatasha wrote:
>>> I have been stuck on this problem for a while - can someone help me
>>> figure
>>> this out? For the following instruction, the instruction set manual says
>>> it should take 5 clock cycles, whereas according to my measurements using
>>> an oscilloscope, I should get 4 clock cycles. What could be the reason
>>> for
>>> the difference? I am using TelosB.
>>>
>>> add #1, -4(r4)
>>
>> How are you measuring its execution time?
>>
>> Have you tried:
>> add #9, -4(r4)
>> and:
>> add #1, -12(r4)
>
> This exercise totally baffles me. How can you precisely and directly measure a
> single instruction execution time? There are numerous ways to indirectly
> measure it and calculate a probable mean.
I sidestepped the issue and offered a hint to the OP as to what he might
want to consider by way of understanding the "discrepancy" in the *posted*
example and his assumptions regarding it's execution time.
[Note the deliberate changes I made to *that* instruction -- without
introducing yet another instruction candidate]
As to measuring a specific instruction's execution time, that depends
a lot on the processor in question and the encompassing instruction stream
(hot/cold cache, emptied pipeline, etc.)
Reply by John Speth●February 28, 20172017-02-28
On 2/24/2017 12:22 PM, Don Y wrote:
> On 2/24/2017 6:52 AM, arshadnatasha wrote:
>> I have been stuck on this problem for a while - can someone help me
>> figure
>> this out? For the following instruction, the instruction set manual says
>> it should take 5 clock cycles, whereas according to my measurements using
>> an oscilloscope, I should get 4 clock cycles. What could be the reason
>> for
>> the difference? I am using TelosB.
>>
>> add #1, -4(r4)
>
> How are you measuring its execution time?
>
> Have you tried:
> add #9, -4(r4)
> and:
> add #1, -12(r4)
This exercise totally baffles me. How can you precisely and directly
measure a single instruction execution time? There are numerous ways to
indirectly measure it and calculate a probable mean.
JJS
Reply by Boudewijn Dijkstra●February 28, 20172017-02-28
Op Fri, 24 Feb 2017 14:52:51 +0100 schreef arshadnatasha
<119076@embeddedrelated>:
> Hi all:
>
> I have been stuck on this problem for a while - can someone help me
> figure
> this out? For the following instruction, the instruction set manual says
> it should take 5 clock cycles, whereas according to my measurements using
> an oscilloscope, I should get 4 clock cycles. What could be the reason
> for the difference? I am using TelosB.
>
> add #1, -4(r4)
Have you measured other instructions, like NOP?
--
(Remove the obvious prefix to reply privately.)
Gemaakt met Opera's e-mailprogramma: http://www.opera.com/mail/
Reply by Tauno Voipio●February 25, 20172017-02-25
On 24.2.17 22:20, Tim Wescott wrote:
> On Fri, 24 Feb 2017 07:52:51 -0600, arshadnatasha wrote:
>
>> Hi all:
>>
>> I have been stuck on this problem for a while - can someone help me
>> figure this out? For the following instruction, the instruction set
>> manual says it should take 5 clock cycles, whereas according to my
>> measurements using an oscilloscope, I should get 4 clock cycles. What
>> could be the reason for the difference? I am using TelosB.
>>
>> add #1, -4(r4)
>
> You don't say what processor.
>
> If it's pipelined, it's going to be hard to assign a one-and-only number
> of clock cycles, because the number taken will depend on _everything_.
>
The TelosB data sheet says that the processor is a MSP430 8 MHz.
--
-TV
Reply by Don Y●February 24, 20172017-02-24
On 2/24/2017 6:52 AM, arshadnatasha wrote:
> I have been stuck on this problem for a while - can someone help me figure
> this out? For the following instruction, the instruction set manual says
> it should take 5 clock cycles, whereas according to my measurements using
> an oscilloscope, I should get 4 clock cycles. What could be the reason for
> the difference? I am using TelosB.
>
> add #1, -4(r4)
How are you measuring its execution time?
Have you tried:
add #9, -4(r4)
and:
add #1, -12(r4)
Reply by Tim Wescott●February 24, 20172017-02-24
On Fri, 24 Feb 2017 07:52:51 -0600, arshadnatasha wrote:
> Hi all:
>
> I have been stuck on this problem for a while - can someone help me
> figure this out? For the following instruction, the instruction set
> manual says it should take 5 clock cycles, whereas according to my
> measurements using an oscilloscope, I should get 4 clock cycles. What
> could be the reason for the difference? I am using TelosB.
>
> add #1, -4(r4)
You don't say what processor.
If it's pipelined, it's going to be hard to assign a one-and-only number
of clock cycles, because the number taken will depend on _everything_.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
I'm looking for work -- see my website!
Reply by arshadnatasha●February 24, 20172017-02-24
Hi all:
I have been stuck on this problem for a while - can someone help me figure
this out? For the following instruction, the instruction set manual says
it should take 5 clock cycles, whereas according to my measurements using
an oscilloscope, I should get 4 clock cycles. What could be the reason for
the difference? I am using TelosB.
add #1, -4(r4)
---------------------------------------
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