Corporate servers based on the Microsoft NT operating system are between a quarter and a third of the price of Unix systems to set up, according to research by the Gartner Group, with most of the savings coming from cheaper NT database software and lower support costs. But the difference in implementation costs between the two will gradually be reduced over the next four years as Unix database costs fall to NT pricing levels. Gartner believes the differential between the costs of supporting a Unix system and an NT system will remain. The IBM AS/400 system will continue to cost as much as 20% more to implement than rival systems, but the ongoing costs will make up for that premium in overall costs of ownership. Gartner also believes that the power differentials between NT, Unix and AS/400 systems at the high-end will continue to be maintained until the year 2001 at least. For single system image symmetric multiprocessing machines, the AS/400 is comfortably the most competitive system in terms of the numbers of concurrent users it can support, scaling up to 10,000 users by 2001, four times as many as top end NT systems. But Unix systems can and will support the largest databases and are the fastest in terms of raw processing power, in transactions per minute.