soft vs buffer only placement blockages

[JasonJung]

Hey I found out that in ICC there are several types of blockages.
One of them, I am getting confused between two concepts; soft blockages and buffer allowed only blockages

it seems that soft blkg acts same as hard blockages until coarse placement. However buffer allowed blockages place only buf or inv at that stage.
I know that optimization cell is inserted inside soft blockages while opt stage.
What i am concerned is, when coarse placing the optcells (that were inserted before pnr; it could be synthesis) cannot be placed in side soft blockages!!
Will this matter in qor anyway?
or is there any considerations while selecting blockages between soft and buffer only allowed ?
(any rules of thumbs or something? things kind of when to use what)

 

[ThisIsNotSam]

the terminology used by ICC is a little odd to me, but I think the buffer only blockage exists to make a distinction between zones where logic blocks should go and zones where long buses should go.

 

[Ashokb431]

Hey I found out that in ICC there are several types of blockages.
One of them, I am getting confused between two concepts; soft blockages and buffer allowed only blockages

it seems that soft blkg acts same as hard blockages until coarse placement. However buffer allowed blockages place only buf or inv at that stage.
I know that optimization cell is inserted inside soft blockages while opt stage.
What i am concerned is, when coarse placing the optcells (that were inserted before pnr; it could be synthesis) cannot be placed in side soft blockages!!
Will this matter in qor anyway?
or is there any considerations while selecting blockages between soft and buffer only allowed ?
(any rules of thumbs or something? things kind of when to use what)

Generally for soft blockages there is no flexibility to mention blocked percentage of cells, but for allow_buffer_only placement blockages there is a flexibility to mention the percentage of cells like if we mention 70% as -blocked_percentage, then buffer and inverters will occupy 30%.