Which is a better aspect ratio?

[masummist]

I need to know the convenient value of aspect ratio that is better for a block in a chip.

If I design a block with the following ways
1. aspect ratio = 1
2. aspect ratio < 1
3. aspect ratio > 1

Which will be better for my design ???

Thanks

 

[pavanks]

Always square is the best floorplan. That is aspect ratio equal to one.
But rarely u get one if ur working on sub blocks.

 

[erikl]

"square is the best" - as pavanks told above - in terms of least mismatch. But there might be a higher priority: the block should fit into the full chip as to achieve a minimum die size. So an optimized global floorplan of the chip could advice an aspect ratio different from the 1:1 ratio.

 

[dick_freebird]

I have never found a useful general rule.

If you have a standard cell type arrangement there is
often more value in laying out to a single-rack height
(conserving routing channels) than in making it look
square by occupying multiple racks (and rack pitch
may change later driven by higher level routing).

On high pin count designs you may not care at all
about core packing density (I/O-bound) or the aspect
ratio of sub-blocks.