Prime Computer Inc, Natick, Massachusetts yesterday added two mid-range models to its family of minicomputers designed for use in an office environment. The 4150, rated at up to 4.1 MIPS, replaces the 3.4 MIPS 9755, which needed a computer room environment, while the 4050 superminicomputer, rated at 2.8 MIPS, replaces the 1.6 MIPS 2755, and like it supports up to 128 terminals. However the 4150 supports up to 254 compared with 192 on the 9755. Each comes in a desk-high cabinet, and is aimed at departmental and workgroup computing. The feature a new three board CPU implementing a five-stage instruction pipeline and incorporate an internal diagnostic processor that tests and continuously monitors the system. The processors are implemented in a combination of semi-custom and merchant TTL, ECL and CMOS parts, each of the components being chosen to achieve optimum balance of performance, low price and small size. Prime’s tests show that the 4150 has 60% to 160% better performance and the 4050 40% to 95% better performance than the 2755, the previous biggest Prime model aimed at the office. Main memory goes to 32Mb on each, and there is a two-set 128Kb cache. The new 4000 series joins the office-installable desk-side 2350, 2450 and 2455. The 4150 is available immediately worldwide, the 4050 will be available in limited quantities this quarter. A 24Mb 4150 with 496Mb disk, PT250 system console and PrimOS licence is $191,600. A 16Mb 4050 and the same disk and console is $88,000. Prime also has a new 4587 GCR office tape drive.