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clock tree quality

Rajesh Vembu

What are the metrics (physical and timing-related) that determine if the clock tree built is robust and of good quality?

If i want to compare the clock tree quality built using 2 different clock tree spec files, what would be the steps to follow?

It should be noted that the AutoCTSRootPin definitions in the 2 spec files could be different, hence a one-to-one comparison of the clock tree report (generated using reportClockTree) won't be helpful.

 - Rajesh

Parents

  •  Hi everyone,

    This seems to be an interesting topic! All the metrics you mentioned so far (both of you), are indeed quite important. Usually we are concerned about timing closure and our designs actually being functional that we tend to forget that the clock tree is the major contributor of dynamic power consumption. So, in a design where power consumption is a hard constraint, I would perform IR drop analysis to the two designs and estimate their power consumption using a common VCD file.

     As another experiment, I would run the same test but this time instead of using buffers for the clock tree I would use inverters (generally smaller, faster and less power-hungry than buffers) and see what happens.

     

    -Alex

     

     

Reply

  •  Hi everyone,

    This seems to be an interesting topic! All the metrics you mentioned so far (both of you), are indeed quite important. Usually we are concerned about timing closure and our designs actually being functional that we tend to forget that the clock tree is the major contributor of dynamic power consumption. So, in a design where power consumption is a hard constraint, I would perform IR drop analysis to the two designs and estimate their power consumption using a common VCD file.

     As another experiment, I would run the same test but this time instead of using buffers for the clock tree I would use inverters (generally smaller, faster and less power-hungry than buffers) and see what happens.

     

    -Alex

     

     

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