[SOLVED] Floorplan: Aspect ratio

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rohit_singh1

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Hi All,

I understand the definition of aspect ratio w.r.t. floorplan, but I am finding it difficult to understand the following example that I found in a book:


Normally, METAL1 is used up by the standard cells. Usually, odd
numbered layers are horizontal layers and even numbered layers are
vertical. So for a 5 layer design, AR = 2/2 = 1.
b. Example2: For a 6 layer design, AR = 2/3 = 0.66
Click to expand...

How/why did you get those numbers (AR = 2/2 , AR = 2/3) is my question.

Thanks!
 
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metal1,3,5 horizontal
metal2,4,6 vertical

metal1 is not usable, so if you have 5 layers, for routing resource, you have metal 2,3,4 5 available, i.e. the resource on horizontal direction (2 metal layers) and vertical direction (2 metal layers) is the same, and AR = 2/2 =1; if you have 6 layers, you have metal 2,3,4,5,6, which means vertical direction (2,4,6) has more resource that horizontal(3,5). If you make horizontal direction wider, ie. AR = 2/3, then you make the routing resource roughly the same for both directions. Make sense?
 
Awesome. Makes total sense. Thanks!!!
 

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