Fmax Improvment

The usual way to improve timing is reduce the amount of logic between registers. Use tier quest to find the worst paths and reduce the logic. Then improve this paths and keep on working on the next worry paths.

With afmax if 140 I suspect you have probably got large accounts of logic between the regs. For 300mhz you'll need a max of 1-2 puts between regs and extra registers around rams and dsps as these can often be bottlenecks.

Summary.. Add more pipelining