IBM Corp’s Ambra Computer Corp unit in the US yesterday announced that it is introducing a new line of six 80486-based portable computers, the SN series and N series, aimed at different segments of the mobile market, but its start in the US has been far from trouble-free: according to PC Week, it has suffered from component shortages, delivery delays and limited telemarketing support; it has already dropped Merisel Inc as the agent for its telephone sales operations due to order-processing problems, and has switched to Insight Direct Inc of Phoenix, Arizon; industry analysts reckon it is shipping 5,000 to 7,000 machines a month, which would leave it way short of its target of 180,000 machines in its first year; the Pentium tower announced in August was finally shipped last week, and an active-matrix colour notebook, introduced at the same time has not been shipped as yet.