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Visitor erikamgard
Visitor
781 Views
Registered: ‎04-05-2018

Intelligent clock gating issues

Hello! 

 

I'm trying to understand and implement clock gating to see how it affects power consumption in an example design .It's unclear to me if I have to add any logic myself, or if I simply have to check the "power opt design" in the implementation settings.

Checking this box seem to add logic gates which I presume is the clock enable logic, however it doesn't affect the power consumption at all. Is there something I'm missing?

 

Best regards 

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4 Replies
Moderator
Moderator
725 Views
Registered: ‎09-18-2014

Re: Intelligent clock gating issues

Erikamgard,

 

 

As with most RTL level power saving techniques, clock gating effectiveness is dependent on your design. So generally if your clock load is small clock gating will not save you much power. So say if you have a shallow design, clock gating will not be as effective as you think. On the other hand, if you have a design with large clock loads, for example,  a BRAM heavy design, you will see a much bigger impact on power. I am guessing that your design is not sufficiently large enough to see a noticeable difference in power saving from intelligent clock gating or your design is already well optimized. 

 

Have a read of WP370 if you haven't already. A lot of good info about intelligent clock gating. 

 

 

Regards,

T

 

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Visitor erikamgard
Visitor
658 Views
Registered: ‎04-05-2018

Re: Intelligent clock gating issues

Thanks for the response tenzinc, 

 

My design has utilizes 45.5/50 BRAM which i consider to be pretty high. The clock stand for 10% of the whole power of the design, which is 0,078 W, which might not be considered alot. Should I not be seeing at least a decrease when activating intelligent clock gating?

 

regards ,erik

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Moderator
Moderator
646 Views
Registered: ‎09-18-2014

Re: Intelligent clock gating issues

Erikamgard,

 

What device are you using? What Vivado version? Like I said generally for small, well optimized/pipelined designs clock gating will have little to no effect... 

 

Regards,

T

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Visitor erikamgard
Visitor
626 Views
Registered: ‎04-05-2018

Re: Intelligent clock gating issues

Hello again,

 

I'm using an Artix-7 XC7A35T-1, Vivado version 2018.1. I could see a decrease from 0,855 W to 0,851 W, which is something I guess.

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