Chipmaker AMD issued a fourth quarter profit warning yesterday, which follows just days after that of rival Intel.AMD blamed the downturn on poor PC sales in the US, which also affected the fourth quarter predictions of Gateway and Apple. Earnings per share are now expected to stand at 50 to 60 cents, down from analyst predictions of 67 cents per share. Chip shipment for the quarter is expected to be slightly higher than the 6.8 million shipped in the third quarter. It had previously been predicted that eight to nine million chips would be shipped this quarter. Company executives said in a statement they did not expect fourth quarter earnings to be down on third quarter revenue of $1.2bn. Fourth quarter results are due for release on January 16.