...equal shares of the market. All three versions of Unix conform to the standards set by the Open Group's Single UnixSpecification and can run on other "qualified" hardware, though not necessarily with the full range of features provided by...
http://www.computerweekly.com/Articles/2007/12/18/228653/hot-skills-aix-6.1.htm
...system supports the specifications defined by the Large File Summit (LFS), a set of extensions to the Single UNIXSpecification (SUS) that support 64-bit filesystems on 32-bit systems. The Veritas filesystem (VxFS) supports large files...
http://www.sco.com/products/openserver6/technical_whitepaper.pdf