This feature enables the usage of the external OS-dependent compression tools like tar, gzip, bzip, pbzip (available on Windows via Cygwin). Basically you can use almost the same compression algorithms/archives as with the built-in Internal PHP compression toolchain feature. So what’s the catch you would ask? Well, the main advantage of this add-on is that it allows the usage of some multi-processor compression tools like PBZip2. By using PBzip2 you get almost linear speed improvements on multi-CPU and multi-core computers (ie. on a computer with 8 CPU the compression may run 8 times faster).