the last month of each quarter, we may not be able to reduce our inventory purchase commitments in a timely manner in response to customer cancellations or deferrals.



Charges to cost of sales for inventory provisions totaled $50.1 million, $89.9 million and $53.0 million, unfavorably impacting our gross margin by 1.2%, 2.1% and 1.3%, in fiscal years 2014, 2013 and 2012, respectively. Sales of inventory that was previously written-off or written-down totaled $43.4 million, $53.7 million and $71.1 million, favorably impacting our gross margin by 1.1%, 1.3% and 1.8% in fiscal years 2014, 2013 and 2012, respectively. As a result, the overall net effect on our gross margin from charges to cost of sales for inventory provisions and sales of items previously written-off or written-down was a 0.1% unfavorable impact in fiscal year 2014, a 0.8% unfavorable impact in fiscal year 2013 and a 0.5% favorable impact in fiscal year 2012.

During fiscal years 2014, 2013 and 2012, the charges we took to cost of sales for inventory provisions were primarily related to the write-off of excess quantities of certain older generations of GPU and Tegra Processor products whose inventory levels were higher than our updated forecasts of future demand for those products. As a fabless semiconductor company, we must make commitments to purchase inventory based on forecasts of future customer demand. In doing so, we must account for our third-party manufacturers' lead times and constraints. We also adjust to other market factors, such as product offerings and pricing actions by our competitors, new product transitions, and macroeconomic conditions - all of which may impact demand for our products.



Please refer to the Gross Profit and Gross Margin discussion below in this Management's Discussion and Analysis for further discussion.



Warranty Liabilities



Cost of revenue includes the estimated cost of product warranties that are calculated at the point of revenue recognition. Under limited circumstances, we may offer an extended limited warranty to customers for certain products.  Our products are complex and may contain defects or experience failures due to any number of issues in design, fabrication, packaging, materials and/or use within a system. If any of our products or technologies contains a defect, compatibility issue or other error, we may have to invest additional research and development efforts to find and correct the issue.   In addition, an error or defect in new products or releases or related software drivers after commencement of commercial shipments could result in failure to achieve market acceptance or loss of design wins. Also, we may be required to reimburse customers, including our customers’ costs to repair or replace products in the field.

     

Income Taxes

We recognize federal, state and foreign current tax liabilities or assets based on our estimate of taxes payable or refundable in the current fiscal year by tax jurisdiction. We recognize federal, state and foreign deferred tax assets or liabilities, as appropriate, for our estimate of future tax effects attributable to temporary differences and carryforwards; and we record a