The original Sun Ultra series was a series of UltraSPARC-based computer workstations and servers developed and sold by Sun Microsystems from 1995 to 2001. The Ultra series introduced the 64-bit UltraSPARC processor and in later versions, lower-cost PC-derived technology, such as the PCI and ATA buses (the initial Ultra 1 and 2 models retained the SBus of their predecessors). The Enterprise 220R is an Ultra 60 motherboard in a rackable server chassis with hot-swappable power supplies. Similarly, the Enterprise 420R is an Ultra 80 motherboard in a server chassis. From CompuWiki, a Wikia wiki.