Financial instruments that potentially subject us to concentrations of credit risk consist principally of investments in debt instruments, derivative financial instruments, and trade receivables. We also enter into master netting arrangements with counterparties when possible to mitigate credit risk in derivative transactions subject to ISDA agreements.

We generally place investments with high-credit-quality counterparties and, by policy, limit the amount of credit exposure to any one counterparty based on our analysis of that counterparty's relative credit standing. Substantially all of our investments in debt instruments are with A/A2 or better rated issuers, and the majority of the issuers are rated AA-/Aa2 or better. Our investment policy requires all investments with original maturities of up to six months to be rated at least A-1/P-1 by Standard & Poor's/Moody's, and specifies a higher minimum rating for investments with longer maturities. For instance, investments with maturities of greater than three years require a minimum rating of AA-/Aa3 at the time of investment. Government regulations imposed on investment alternatives of our non-U.S. subsidiaries, or the absence of A rated counterparties in certain countries, result in some minor exceptions. Credit rating criteria for derivative instruments are similar to those for other investments. The amounts subject to credit risk related to derivative instruments are generally limited to the amounts, if any, by which a counterparty's obligations exceed our obligations with that counterparty. As of December 27, 2008, the total credit exposure to any single counterparty did not exceed $500 million. We obtain and secure available collateral from counterparties against obligations, including securities lending transactions, when we deem it appropriate.

A substantial majority of our trade receivables are derived from sales to original equipment manufacturers and original design manufacturers. We also have accounts receivable derived from sales to industrial and retail distributors. Our two largest customers accounted for 38% of net revenue for 2008 and 35% of net revenue for 2007 and 2006. Additionally, these two largest customers accounted for 46% of our accounts receivable as of December 27, 2008 and 35% of our accounts receivable as of December 29, 2007. We believe that the receivable balances from these largest customers do not represent a significant credit risk based on cash flow forecasts, balance sheet analysis, and past collection experience.

We have adopted credit policies and standards intended to accommodate industry growth and inherent risk. We believe that credit risks are moderated by the financial stability of our major customers. We assess credit risk through quantitative and qualitative analysis, and from this analysis, we establish credit limits and determine whether we will seek to use one or more credit support devices, such as obtaining some form of third-party guaranty or standby letter of credit, or obtaining credit insurance for all or a portion of the account balance if necessary.

We continually monitor the credit risk in our portfolio and mitigate our credit and interest rate exposures in accordance with the policies approved by our Board of Directors. We intend to continue to closely monitor future developments in the credit markets and make appropriate changes to our investment policies as deemed necessary.