Hewlett-Packard Co yesterday filled out the middle of its proprietary HP 3000 computer line with the HP 3000 series 987/200, a symmetrical multiprocessing system that extends the performance of the 9X7 family. The new model supports up to 1,700 simultaneous users, and is available in both four-slot and 12-slot configurations with shipments set for the first half of next year. The series 987/200RX four-slot configuration will cost $188,320, and the 987/200SX 12-slot configuration will be $214,820, with 64Mb memory and 1Gb of disk in each case. The machine, which runs the MPE/ix operating system, uses two 96MHz HP PA-7100 RISCs; the machine is 90% faster than the Series 987 boxes, six times faster than Series 917.