Shares of Rackable Systems ( RACK) plummeted in late trading Thursday after the company's weak guidance offset better-than-expected second-quarter earnings. The maker of servers and storage systems posted second-quarter earnings of $5.3 million, or 18 cents a share, down from with $1.2 million, or 7 cents a share, a year ago. Excluding items, earnings rose to $8.1 million, or 28 cents a share, from $2 million, or 12 cents a share, a year ago. Revenue increased 5% to $88.6 million. Analysts polled by Thomson First Call expected earnings of 22 cents a share, before items, on revenue of $84.3 million. However, the company forecast third-quarter revenue of $80 million to $85 million in its conference call, according to Briefing.com, and warned that it sees declines in the server market. Analysts predict third-quarter revenue of $84.3 million. Shares tumbled $10.41, or 30%, to $24.50 after hours. On Semiconductor ( ONNN) beat Wall Street's second-quarter earnings expectation, sending shares higher after hours. The company earned $67.5 million, or 19 cents a share, up from $13.5 million, or 5 cents a share, a year ago. The latest quarter's results include restructuring charges of about $3.3 million, or 1 cent a share. Analysts predicted earnings of 13 cents a share. Sales rose to $375.3 million from $302.8 million a year ago, topping Wall Street's forecast of $354.53 million. Looking ahead, On Semiconductor forecast third-quarter sales of $405 million to $415 million, which is well above analysts' forecast of $372 million. Shares advanced 43 cents, or 7.1%, to $6.52 in after-hours trading. Genesis Microchip ( GNSS) soared after the company beat Wall Street's fiscal first-quarter earnings expectations. The company earned $1.4 million, or 4 cents a share, down from $2.1 million, or 6 cents a share a year ago. Excluding items, Genesis Microchip earned 11 cents a share in the June quarter. Revenue totaled $55.9 million, down from $59.8 million a year earlier. Analysts were looking for break-even earnings and revenue of $57.9 million. Genesis forecast fiscal second-quarter revenue of $67 million to $72 million. Analysts predict revenue of $67.3 million. Shares jumped $2.34, or 21%, to $13.55 after hours.