The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( Trefis) -- While AMD ( AMD) lives in the shadow of Intel ( INTC) in the PC microprocessor market, it competes neck-and-neck with Nvidia ( NVDA) in the discrete graphics processing unit space. AMD has a market share of close to 50% in the business of supplying discrete GPUs for notebooks. Going forward, the company will not only benefit from the growth in global notebook shipments, but also from an increase in discrete GPU penetration in notebooks. We estimate that the discrete notebook GPU business constitutes about 12% to AMD's stock. Let's take a look below at why this penetration will increase. See our complete analysis for AMD. Discrete GPUs in notebooks (sold as a percent of notebook shipments) increased from 25% in 2005 to 33% in 2011. We expect this to steadily increase to close to 46% by the end of our forecast period, close to the figure witnessed for desktop GPUs.