原创 海外捉虫记—前紧后松，给设计留些缓冲

这个冗余确实不小哦。。。10%！ 一般多少合适呢？不知道有没有平均水平的说法，我们通常多一点点，比如125MHz需求，设置到128MHz就OK了 找了n久，没找到官方说法。xilinx建议有多少约束多少:) Xilinx recommends that you specify the exact value required for a path, as opposed to over-tightening a specification. Specifying tighter constraints than required is not recommended. Tighter constraints can lengthen PAR runtimes and cause degradation in the quality of results. --from http://www.cis.upenn.edu/~milom/cse372-Spring06/xilinx/cgd.pdf mengyudn