and the P400 ran PRIMOS 4. It ran a V-mode instruction set, along with the S-mode and R-mode instructions. It had a segmented virtual memory architecture, somewhat similar to Multics. 1979: Prime 450, 550, 650, 750—the beginning of the 50 series nomenclature The Prime 550 was an upgrade in performance over the Prime 400. It ran at 0.7 MIPS, had up 2 MB of memory and 500 MB of disc storage and a 9-track tape unit. The Prime 750 was a major upgrade. It ran at 1.0 MIPS, had 2–8 MB of memory and 1200 MB of disc storage and a 9-track tape unit. This was very competitive with a similarly priced DEC VAX-11/780 and was one of the first 32-bit superminicomputers. Prime 750 systems were installed at Rensselaer Polytechnic Institute (RPI), Rutherford Appleton Laboratory (RAL), University of Paisley, Leeds University, Scripps Institution of Oceanography (SIO), University of Rhode Island, University of Manchester Institute of Science and Technology (UMIST), the CADCentre in Cambridge, and Southeastern University in Washington, DC. PRIMENET and a local area networking software product named RINGNET were announced. 1980: Prime 150 and 250 1981: Prime 850 (dual CPU machine) Prime also marketed MEDUSA CAD software. 1982: Prime 2250 also known internally as "Rabbit" 1983: Prime 9950 1984: Prime 2550, 9650, 9750 1985: Prime 9955, 9655, 2655 The 9955 ran at 4.0 MIPS, had 8–16 MB of memory and 2.7 GB of disc storage and a 9-track tape unit. Five Prime 9955 computers (uk.ac.salford.sysa to .syse, connected to JANET) were installed at the University of Salford (along with other systems such as the 2250, 2550, and 750); a Prime 9955 was installed at UMIST and a Prime 9655 at Nottingham University. 1986: Prime 2350, 2450, 9755, and 9955-II 1987: Prime 2455, 2755, 6350, and 6550 1989: Prime 2850, 4050, 6450, and 6650 1990: Prime 2950, 4150, and 6150 By 1987, Prime Computer had introduced an alternative line of Intel 80386-based computers, the EXL-316 series, running the Unix operating system. A "new line of Unix-based EXL-7000 computers" was announced in late 1990. The company was successful in the 1970s and 1980s, peaking in 1988 at number 334 of the Fortune 500. In 1985 the company was the 6th largest in the minicomputer sector, with estimated revenues of US $564 million Much of this was based on the US Banking industry where the Prime Info database was widely accepted. As