> With a large counter, addition of the highest bit has to wait for completion of the previous one, etc. so if this takes longer than one clock cycle you have

> With a large counter, addition of the highest bit has to wait for completion of the previous one, etc. so if this takes longer than one clock cycle you have to implement a different, pipelined addition algorithm. (Or run everything at lower clock frequency.) Kogge Stone carry lookahead. You can calculate the upper bits in parallel using Kogge-stone (which is the predecessor to what GPU programmers call "prefix-sum" parallelism)