Slackware

Slackware is a popular Linux distribution for x86 systems, widely considered to be the oldest surviving distribution. A significant portion of Ultima Linux, including package management, is based on Slackware, but lately most of the code is either independently developed by the Ultima developers or borrowed from Slamd64.

Although Slackware is still heavily popular, it does not natively support 64-bit systems, hence the need for ports such as Slamd64.