Dell Inc. said Monday that it will close its desktop computer manufacturing plant in North Austin by the end of the year, cutting 900 local jobs as part of a global effort to reduce costs. The factory that will be closed is the Topfer Manufacturing Center, which has been a showplace Dell factory since the late 1990s. The facility, on Howard Lane east of Interstate 35, makes mostly desktops for commercial customers. A nearby plant that makes servers will remain open. The plant closing is the biggest job hit at Dell in Central Texas since the company cut more than 5,700 jobs during the tech downturn in 2001.