This is more of a computing question, but only electronics geeks would know such things. Today's computers use multiple layers of memory in order to work with data quickly. Currently CPU speeds are anywhere from 10 times to 100 times faster than RAM memory. Therefore, CPUs are built with a small amount of very fast memory (Static RAM, or SRAM) which is usually from 10 KB to 10 MB in size. Data cached in this memory is the fastest to work with and DDR RAM is usually much slower (10-100 times).
Wikipedia says DDR3 RAM currently takes 5-10 ns per "cycle". What does this mean exactly, and how fast is SRAM in comparison? Also, for embedded projects utilizing FPGA's, how useful is SRAM and DDR3 and can either be omitted in favor of the other? (eg. No need of SRAM if DDR3 speeds are similar)