Updated from April 20Applied Micro Circuits ( AMCC) narrowed its loss and more than doubled fourth-quarter revenue, the San Diego-based chipmaker said after the close Tuesday. Applied Micro shares were recently up 49 cents, or 9.3%, to $5.79. Wednesday morning, CIBC World Markets upgraded its rating on the stock to sector perform from sector underperform. The company lost $2.1 million, or 1 cent a share, compared to a year-ago loss of $229.1 million, or 76 cents a share, according to generally accepted accounting principles. Net revenue was $47.4 million, up from $20.1 million a year ago. Excluding charges, the company broke even on a per-share basis for the first time in more than a year. Analysts polled by Thomson First Call were expecting the company to lose 1 cent on sales of $44.85 million. For the full fiscal 2004, the company posted a GAAP loss of $104.9 million, or 34 cents a share, on sales of $131.2 million; in 2003 the company lost $2.47 a share on sales of $101.6 million. Applied Micro Circuits makes chips used in networking hardware and storage networks.