what is clock feedthrough
clock feed through concept is applicable wen u do design partition.
assume u have 2-3 partitions in ur design and now if the clk for the second partition hs to go thru the first partition, then the tool doesnt know which is the source or root pin of the clk for the second partition, then u need to specify the clock as a "feed thru" clock in the first partition !
i,e in effect, instead of the clk directly goin thru to the 2nd partition, the 1st partition now feeds the clk thru ( goes thru) to the 2nd one.
If there is no other go, then feed thru option is the one. Else re-do the design partition such tht the clock is not fed- thru the 1st partition to the 2nd one !!!
PS:
CDU - clock distribution unit is placed such tht the clk for the second partition has to go thru the one or more partitions in the design
WBR
Lakshman