Once people are hooked on the Macintosh, they can’t get enough of the things it seems – among the 200 largest sites using the Apple Computer Inc machines in the US, the number installed has doubled in 20 months, according to MacWeek, which commission Field Research to conduct a survey, which found that the biggest customers account for 325,000 US Macs, 11% of the total domestic base; 28 sites were identified with more than 3,000 Macs and based on purchase plan estimates of MacWeek 200 managers, total installed Macs will outnumber MS-DOS boxes at these sites within months; top of the tree is the University of Texas at Austin with 9,006 Macs, while the top manufacturing site was Hughes Aircraft in Long Beach, California, with 7,500; even Tektronix Inc, which makes workstations itself, has 4,805 of the things, and Eastman Kodak, Honeywell, Boeing, McDonnell, GTE and Peat Marwick each has more than 3,500 Macs; manufacturing sites accounted for 39% of the population, service 17% and government, 6% with education making up the balance.