windows 1KHz time loop limitation reason

[Ali211]

I am using timed loop in Labview2011 . I am not able to operate the time loop above 1kHz or less than 1 msec .i read in some answer on the forum that due to windows it is not possible to operate above 1kHz but reason was not given .i want to know Why windows can not operate time loop above 1kHz ?

Yours sincerely

[JÞB]

The only timing source required by Windows is the millisecond timer.  Therefore the timed loop will default to using that clock limiting the timed loop to millisecond resolution.  Windows DOES support a precision timer that can be used to control the average loop rate with higher resolution HOWEVER, this does not solve many problems since it is still non-deterministic And, you loose the timed loops unique execution system (reserved Threadpool)  worse, it introduces a variable resolution on different hardware (Not all precision timers operate at the same clock rate)

But you can read more about timing in this community nugget.

[Ali211]

Thanks for Answering.

i have been trying . i wanted to run timed loop at micro sec period. It is possible by using TARGRTING PC in Labview but i just want to know why windows con not operate in Mhz in Labview time loops.

Your sincerely ,

[billko]

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@Ali211 wrote:

Thanks for Answering.

i have been trying . i wanted to run timed loop at micro sec period. It is possible by using TARGRTING PC in Labview but i just want to know why windows con not operate in Mhz in Labview time loops.

Your sincerely ,

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You can find the answer to this in Jeff's reply here.

[krivan]

If you wanna try the LabVIEW Real-Time Module and building a desktop real-time target, etc., this might be helpful for you.

http://sine.ni.com/cs/app/doc/p/id/cs-14703 

[Ali211]

I am working with Labview RT and i know about PC targeting configuration But i dont know the reason behind windows limitaion of 1KHz at max?

Yours sincerely

[krivan]

As billko already said, your answer is in Jeff's reply above.

Thus if you want to go to the microsecond range, you need to use a real-time operating system that you can download from NI websites. And you wanna use the RT LabVIEW with that real time system.

[Ben · Accepted solution]

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@Ali211 wrote:

I am working with Labview RT and i know about PC targeting configuration But i dont know the reason behind windows limitaion of 1KHz at max?

Yours sincerely

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The issue is the clock source.

I have used a hardware clock (an NI DAQ device with a built in clock) to drive a timed loop at 2KHz but that was only possible using a hardware clock.

For the MHz cycle rates you mentioned above, you will have to move to an FPGA to get that type of perfromance.

As to WHY?

Stepping into the "way-back-machine" and setting the target date for about 1979 we find that PC came equiped with keyboads but a mouse was an add-on. If you added a mouse you found that 50% of your CPU was used every time you moved the mouse. Since all we had was DOS back then no big deal. Moving forward in time to Windows 3.1 we are still running on top of DOS but we could now use a mouse.

Now to make it look like the mouse cursor was keeping up with the mouse moves, interputs were firing repeatedly and teh screen needed updated as quickly as possible. SO it turned out that using an SO clock that fire a 1 KHz was fast enough to keep up with the mouse.

Windows was designed to use a 1KHz clock and until MS decides to use a faster clock, we have to lieve in that environment... unless you abandon Windows and move to another OS.

Ben

[billko]

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@Ben wrote:

<snip>

Stepping into the "way-back-machine"...

<snippety-snip>

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Wonder if anyone knows/remebers what the "way-back machine" is any more, or does is the knowledge lost when we go, Ben?

[crossrulz]

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@billko wrote:

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@Ben wrote:

<snip>

Stepping into the "way-back-machine"...

<snippety-snip>

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Wonder if anyone knows/remebers what the "way-back machine" is any more, or does is the knowledge lost when we go, Ben?

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Don't worry, I see little kids watching Bullwinkle (and therefore Peabody with his boy Sherman).