1. A system for detecting a pattern in a data stream comprising: a FIFO for receiving an N-bit wide data stream and a corresponding first clock signal at a first rate, and outputting the data stream as a W times N-bit wide data stream and a corresponding second clock signal at a second rate, where W is an integer natural number and the second rate equals the first rate divided by W; a bus splitter for splitting the W times N-bit wide data stream into W data streams of width N; a plurality (W) of RAMs, each RAM for storing data obtained by processing the pattern and for receiving a respective one of the data streams of width N as an address and the second clock signal as a clock, and each RAM being operable to output a portion of the data on an M-bit wide output bus in accordance with a value of the address; and a processor for receiving the portions of data on each M-bit wide output bus as data and the second clock signal as a clock, and being operable to determine whether the pattern is in the data stream in dependence upon the received portions of data and the received clock, and for outputting a pattern match signal indicating detection of the pattern in the data stream.