Derate Calculation for Advanced On Chip Variation

[subhash_chevella]

Hi all,

As we know, AOCV calculates the derate values of each cell in the design based on the following two factors.
1. Depth/stage based (to consider Random Variations).
2. Distance/location based (to consider Systematic Variations).

As depth increase for the cell, the derate value will be decrease ie, variation will be less.
Can any one help me in understanding this?
Why variation of the cell delay will be less as depth increases?

thanks for your help.

regards,
Subhash C

 

[subhash_chevella]

Hi,

any updates on this post?
try to help me in understanding this.

regards,
Subhash C

 

[charan teja]

Hi Subhash ,

First let me tell you the difference b/w ocv and Aocv. Hope this clears your doubt.

Ocv adds derates to all the logic b/w two regs or on clock path , but that much pessimism is not necessary to all paths bcz all paths dont have equal logic b/w registers. So we are adding extra pessimism .

Aocv is actually Reducing the pessimism . Path based is while calculating timing the tool checks for the logic depth and then adds the derate . so as the depth increases , the derate factor reduces and so we are not inducing over pessimism in the design .


Regards,

Cherry

 

[subhash_chevella]

Hi Charan,

thanks for the reply.

Ya. I understood this point.
but, I want to understand the below statement/point,
"in AOCV, as the depth increases, the derate factor reduces".
How? & Why?

regards,
Subhash C