facts or circumstances. In addition, we recognize liabilities for potential United States and foreign income tax contingencies based on our estimate of whether, and the extent to which, additional taxes may be due. If we determine that payment of these amounts is unnecessary or if the recorded tax liability is less than our current assessment, we may be required to recognize an income tax benefit or additional income tax expense in our financial statements accordingly.



As of January 25, 2015, we had a valuation allowance of $261.0 million related to state and certain foreign deferred tax assets that management determined are not likely to be realized due, in part, to projections of future taxable income and potential utilization limitations of tax attributes acquired as a result of stock ownership changes. To the extent realization of the deferred tax assets becomes more-likely-than-not, we would recognize such deferred tax asset as an income tax benefit during the period.



Goodwill



Goodwill is subject to our annual impairment test during the fourth quarter of our fiscal year, or earlier if indicators of potential impairment exist, using either a qualitative or a quantitative assessment.  Our impairment review process compares the fair value of the reporting unit in which the goodwill resides to its carrying value.  We have identified two reporting units, GPU and Tegra Processor, for the purposes of completing our goodwill analysis. Goodwill assigned to these reporting units as of January 25, 2015 was $209.7 million and $408.5 million, respectively. Determining the number of reporting units and the fair value of a reporting unit requires us to make judgments and involves the use of significant estimates and assumptions. We also make judgments and assumptions in allocating assets and liabilities to each of our reporting units. We base our fair value estimates on assumptions we believe to be reasonable but that are unpredictable and inherently uncertain.



During the fourth quarter of fiscal year 2015, we elected to use the quantitative assessment to test goodwill for impairment for each reporting unit. In applying the fair value based test of each reporting unit, the results from the income approach and the market approach were equally weighted. These valuation approaches consider a number of factors that include, but are not limited to, prospective financial information, growth rates, terminal or residual values, discount rates and comparable multiples from publicly traded companies in our industry and require us to make certain assumptions and estimates regarding industry economic factors and the future profitability of our business.



When performing an income approach valuation, we incorporate the use of projected financial information and a discount rate that are developed using market participant based assumptions to our discounted cash flow model. Our estimates of discounted cash flow were based upon, among other things, certain assumptions about our expected future operating performance, such as revenue growth rates, operating margins, risk-adjusted discount rates, and future economic and market conditions. Our estimates may