The S&P 500 was down 0.1% in midday trading to 2,096.34.
The Dow Jones Industrial Average was down 0.4% to 17,795.52.
The NASDAQ was up 0.3% to 4,945.94.
The yield on a 10-year Treasury bond was down 0.7% to 1.84%.
The price of gold was flat at $1,217.
Irvine-based Western Digital Corp was up 2.9% to $46.29 and a $13 billion market cap on moderate volume. The storage products maker last week offered 2016 guidance that included its SanDisk Corp. acquisition.
Costa Mesa-based bank holding company Pacific Mercantile Bancorp was down 4.3% to $7.20 and a $165 million market cap on moderate volume.