Sun Microsystems offered a SPARC CPU based Enterprise server in high-end, mid-range and entry level segments.

The original 1995 Enterprise line of servers had humble beginnings. They were based on Suns Ultra line of workstations and shared the same motherboard and Ultra SPARC I processors. These machines, branded as the Ultra Enterprise 1 and 2,  were geared towards the small office or department market segments.

Sun released the entry level Enterprise 250 and Enterprise 450 servers in 1997. Like the Ultra Enterprise servers, these machines were derived from current workstation platforms which offered 2 and 4-way processor configurations and the Unix based Solaris operating system. In less than two years the entry level product refresh brought about the Enterprise 220R and 420R systems. The R designs were, as specified in the model number, exclusively rackmount servers and remained workstation derived. 

It is interesting to note that while PCs are still struggling along with the transition over to 64bit processors, the enterprise segment has been running them for over a decade. 

The mid-range Enterprise offerings from Sun began in 1996 with four machines, the Ultra Enterprise 3K through the Ultra Enterprise 6K. These boxes were successor platforms to Suns existing SPARCserver and SPARCcenter servers. Computing horsepower was derived from UltraSPARC-I and UltraSPARC-II CPUs and ranged from the 6-way 3000 up to 30-way in the 6000.

In 1997 Sun released their 64-way high-end E10K (Enterprise 10000) server for datacenter and scientific computing market segments. Originally this platform was designed by Cray however after a number of acquisitions, ended up giving Sun the high-end offering they wanted to add to their lineup.