FreeBSD 6.1 (AMD64)

FreeBSD provides higher performance and greater compatibility with other operating systems, with less system administration. FreeBSD is a professional quality, UNIX compatible operating system which is the backbone of many of the world's busiest Internet sites.
FreeBSD 6.1 is the next step in the development of the 6.X branch, delivering several performance improvements, many bugfixes, and a few new features. With FreeBSD 6.1 you can expect a UNIX like environment. Some updates with this version are:

• Improved keyboard support
• Improved sound drivers
• A number of base system components have been made multi-processor safe
• IPv6 support in ipfw
• Various network driver bug fixes and enhancements
• Improved package tools, including Portsnap
• A firmware subsystem that allows loading binary blobs into the kernel