Intel in the third quarter padded its share of the worldwide microprocessor market from a year ago, while rival Advanced Micro Devices saw its share fall, a market research firm said Wednesday.

Intel ended the quarter with an 80.4% share of global revenue, up 1.7% from the same period a year ago, iSuppli said. AMD's share on the other hand fell 1.8 percentage points to 12.1% from 13.9% a year ago.

When compared to the second quarter, AMD's results improved. The chipmaker on a sequential basis saw an increase of 0.1 of a percentage point. Intel also had a short-term gain of 0.3 of a percentage point, iSuppli said. The gains were taken at the expense of smaller vendors, which are finding it increasingly more difficult to compete during the global financial crisis.

"Intel's growth is largely due to the strength of its product portfolio in the notebook segment," iSuppli analyst Matthew Wilkins said in a statement. "In the third quarter, Intel achieved a double-positive, producing share growth on both a sequential and year-over basis, while main rival AMD grew in the short term only."

The PC market, a key driver of microprocessor sales, showed healthy growth in the third quarter, despite some signs of weakening demand, iSuppli said. Unit shipments increased from 12% to 14% over the third quarter of 2007, with notebook demand continuing to be the strongest contributor to sales. For the full year, ISuppli forecasts a 12.5% increase in unit shipments over last year.

Among the recent signs of weakness in the PC market is a drop in revenues for the overall semiconductor industry, which supplies microprocessors, system memory and other components. ISuppli this month trimmed its 2008 forecast and warned that the semiconductor market could get much worse if the current global financial crisis worsens.