By Rex Crum

The ongoing battle between EMC Corp. and NetApp Inc. to acquire Data Domain Inc. continued on Monday, and highlighted a mixed trading session for tech stocks.

Before the market opened, EMC (EMC) raised its all-cash bid for Data Domain (DDUP) to $33.50 a share from its previous offer of $30 a share. Data Domain has agreed to be acquired by NetApp (NTAP) for $30 a share in cash and stock, but EMC's new bid may cause Data Domain to re-visit the latest offer.

Data Domain has been in play in late May since it reached a deal to be acquired by NetApp for $25 a share. Since then, NetApp and EMC have increased their offers for the data-services technology company.

Data Domain shares rose 92 cents, or 2.8%, to $34.13 following EMC's latest offer. EMC's stock was down 2 cents a share at $12.77, while NetApp gave up 14 cents a share to fall to $18.82.

With the Data Domain battle leading the day's action, the tech-heavy Nasdaq Composite Index (RIXF) fell 9 points to 1,787. The Morgan Stanley High Tech 35 Index (MSH) was off slightly, but the Philadelphia Semiconductor Index (SOX) edged above its breakeven line.

Decliners included Apple Inc. (AAPL), Microsoft Corp. (MSFT), Oracle Corp. (ORCL), while gains came from Dell Inc. (DELL), Hewlett-Packard Co. (HPQ), IBM Corp. (IBM), Cisco Systems Inc. (CSCO) and Intel Corp. (INTC).