Why another set of cells just for clock exists in library? What's the difference between CK* cells with other base cells?

[Fun-King]

There are CK* cells in library. And There are basic combine logic cells in library.

CKMUX2Dx vs MUX2Dx
CKND2Dx vs ND2Dx
CKOR2Dx vs OR2Dx
...

1. What's the difference?
2. What's the beneficial to use these CK* cells?
3. Do we need to set these cells dont use in synthesis?

 

[ThisIsNotSam]

usually these cells have properties that are better for a clock tree, with balanced fall and rise times. they are still perfectly valid cells to be used anywhere else in your design

 

[Trent_N]

The clock standard cells will have balanced rise times and fall times, but this is not the only benefit of these cells. The clock buffers I have seen use more silicon area and have the transistors spaced farther apart to help to minimize hot spots. The clock signals will toggle more often than the logic signals and require a more robust layout to handle the extra current.