QUESTIONS BASED ON FLOORPLANNING

What is core utilization ?

It is the ratio of (std cell area + macro area + blockage area) / total area

What is cell utilization ?

It is the ratio of std cell area/ total area allocated to standard cells

What is gate count?

Gate count is 3 to 4 times of instance count.

Total placeable instance area / 2 input NAND gate area in .lib

What is aspect ratio ?

It is the ratio of vertical routing resources to the horizontal routing resources.

What is a channel ?

It is the minimum spacing required between two macros or between macros and boundary.

How do you calculate the channel width ?

Based on the fly-line analysis we will able to know the no. of signals passing through the channel and suppose “21” signals are passing than “21” metal routes are required. So if the signal are need to be routed vertically than we divide the no of routes by no of vertical layers. Suppose no of vertical layers is “3”. On each metal layer 7 track are needed so the width of channel should be equal to 7 tracks.

How do you measure the no. of signals passing through a channel ?

Through the fly-line analysis

How do you calculate the the metal routes that can be passed through a channel ?

The no of metal routes required is equal to the no of signal passing through the channel

Guidelines for general macro placement ?

If two communicating macros placed close to each another and if all the pins of both the macros are connected to each other than there is no need of spacing but if some pins are talking with the core logic than we need to provide some spacing so that from the pin route should come and connect to the logic. So minimum spacing required between the 2 macros or boundary and macro is called as the channel.

What is Grid ? Diff kinds of Grid ?

Grids can be of manufacturing grid, placement grid and routing grid. The minimum metal length that can be manufactured is called manufacturing grid. Placement grid is nothing but one SITE whose height is equal to the std cell height and width is multiple of M2 pitch and all the cells are placed according to this grid. During routing tool divides entire area into small square boxes and assigns horizontal and vertical tracks to it and route according to these routing grids.

What is core area ?

The area in which standard cells, memories, blockages, power mesh, routing of nets are present we call it as core area

What do you mean ny a 9Track Cells ?

If there are 9 parallel routing tracks are present in a cell than we call it as 9 track cells.

Typical Metal layers used in Macro ?

Generally M1 to M4 metal layers are used by macros .