Sun Ultra series

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 Ultra workstations and the Ultra Enterprise (later, simply Enterprise) servers replaced the earlier SPARCstation and SPARCcenter/SPARCserver series respectively. The Ultra/Enterprise series itself was later replaced by the Sun Blade (workstations) and Sun Fire (servers) ranges.
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.
The Ultra range were sold during the dot com boom, and became one of the biggest selling series of computers ever developed by Sun Microsystems. Many companies and organisations (including Sun Microsystems) still rely on Sun Ultra products.
The Ultra brand was later revived in 2005 with the launch of the Ultra 20, Ultra 40 and Ultra 45 workstations and the Ultra 3 laptop. Confusingly, the Ultra 20 and 40 are not UltraSPARC-based systems, but are based on AMD64-architecture processors.