Speeding up FPGA clock schemes

What is FPGA?
Short for Field-Programmable Gate Array, a type of logic chip that can be programmed. An FPGA is similar to a PLD, but whereas PLDs are generally limited to hundreds of gates, FPGAs support thousands of gates. They are especially popular for prototyping integrated circuit designs. Once the design is set, hardwired chips are produced for faster performance.

What does asynchronous mean?
In an asynchronous circuit, parts are largely autonomous. They are not governed by any regular, periodic time-controlling mechanism, such as a clock circuit or signal, but instead need only wait for the signals that indicate completion of instructions and operations. These signals are often specified by simple data transfer protocols.
This digital logic design is contrasted with a synchronous circuit which operates according to clock timing signals.