Serial communication the parallel bus's advantage of simplicity (no need for serializer and deserializer, or SerDes) and to outstrip its disadvantages (clock skew, interconnect density). The migration from PCI to PCI Express is an example. Many serial communication systems were originally designed to transfer data over relatively large distances through some sort of data cable. Practically all long-distance communication transmits data one bit at a time, rather than in parallel, because it reduces the cost of the cable. The cables that carry this data (other than "the" serial cable) and the computer ports they plug into are usually referred to with a
NAS Parallel Benchmarks serial versions of the benchmarks consistent with the parallel versions and defined a problem size "Class W" for small-memory systems. NPB 2.4 of 2002 offered a new MPI implementation and introduced another still larger problem size "Class D". It also augmented one benchmark with I/O-intensive subtypes. NPB 3 retained the MPI implementation from NPB 2 and came in more flavors, namely OpenMP, Java and High Performance Fortran. These new parallel implementations were derived from the serial codes in NPB 2.3 with additional optimizations. NPB 3.1 and NPB 3.2 added three more benchmarks, which, however, were not available across all implementations;