Advanced Micro Devices, announced that it will layoff 12% or 1,400 workers as a result of weak computer PC sales. The layoffs will take place over the next several months. This is the third major layoff AMD has had in the last three years. It cut about 7,000 workers in 2008 and 2009.

AMD is facing an industry-wide problem: PC sales growth, particularly in the U.S. and Europe, has been anemic because of the weak economy and competition from smartphones and tablets like Apple’s iPad and iPhones.

AMD’s business is in chips for PCs. It doesn’t have a meaningful presence in smartphones and tablets, where the growth is. Intel is also faced with a similar problem.

The rise of mobile devices, is hurting the old guards like AMD and Intel, and benefiting chip designer ARM Holdings, chip makers such as Qualcomm and Texas Instruments, whose processors consume less power.