Taiwan Semiconductor Manufacturing Company's manufacturing capacity has fallen way short of the demand placed upon it by Qualcomm, AMD, and Nvidia. AMD and Nvidia produce their latest generation GPUs on TSMC's 28nm process and have been having trouble getting the chips to ship. Even though the 7970 launched right at the beginning of the year, they've shipped very few due to the shortages.
Nvidia has launched only one GPU based upon its next generation, 28nm Kepler architecture due to the shortage. Nvida has had to delay launching several more models due to this shortage as they would be unable to provide the silicon to go along with the launch. Qualcomm has been forced to move to foundry to produce its ARM chips for phones and tablets.
All of these shortages are expected to lessen by the end of Q3 2012. Yield rates of the 28nm process are slowly improving and will add to reducing this shortage. More as it comes.