Additionally, sales of our embedded products for entertainment devices and revenue from license fees related to game consoles also decreased during fiscal year 2014. These decreases were partially offset by increased sales of Tegra 4-based products for smartphones and tablet devices, as well as for automotive infotainment systems.



All Other. License revenue from the patent cross licensing arrangement we entered into with Intel in January 2011 was flat at $264.0 million for fiscal years 2015, 2014 and 2013.



Concentration of Revenue



Revenue from sales to customers outside of the United States and Other Americas accounted for 75% of total revenue for both fiscal years 2015 and 2014, and 74% of total revenue for fiscal year 2013. Revenue by geographic region is allocated to individual countries based on the location to which the products are initially billed even if the revenue is attributable to end customers in a different location.



Revenue from significant customers, those representing 10% or more of total revenue for the respective dates, is summarized as follows: 

 

Gross Profit and Gross Margin

 

Gross profit consists of total revenue, net of allowances, less cost of revenue. Cost of revenue consists primarily of the cost of semiconductors purchased from subcontractors, including wafer fabrication, assembly, testing and packaging, board and device costs, manufacturing support costs, including labor and overhead associated with such purchases, final test yield fallout, inventory and warranty provisions and shipping costs. Cost of revenue also includes development costs for license and service arrangements and stock-based compensation related to personnel associated with manufacturing.



Gross margin is the percentage of gross profit to revenue. Our gross margin can vary in any period depending on the mix of types of products sold. Our gross margin is significantly impacted by the mix of products we sell, which is often difficult to estimate with accuracy. Therefore, if we experience product transition challenges, if we achieve significant revenue growth in our lower margin product lines, or if we are unable to earn as much revenue as we expect from higher margin product lines, our gross margin may be negatively impacted.



Our overall gross margin was 55.5%, 54.9% and 52.0% for fiscal years 2015, 2014 and 2013, respectively. The increase over these fiscal years was driven primarily by a richer product mix in our GPU business, partially offset by lower Tegra business margins.



Charges to cost of sales for inventory provisions totaled $59.4 million, $50.1 million and $89.9 million for fiscal years 2015, 2014 and 2013, unfavorably impacting our gross margin by 1.3%, 1.2% and 2.1%, respectively. Sales of inventory that was previously written-off or written-down totaled $32.4 million, $43.4 million and $53.7 million for fiscal years 2015, 2014 and 2013, favorably impacting our gross margin by 0.7%, 1.1% and 1.3%, respectively. As a result, the overall net effect on our gross margin from inventory provisions and sales of items previously written down was an unfavorable impact of 0.6%, 0.1% and 0.8% in fiscal years 2015, 2014