The roiling stock markets have all but closed the IPO window, but tech M&A activity should continue to be strong through the rest of the year.

So says Rob Fisher, leader of PricewaterhouseCooper’s technology M&A group in San Jose, Calif. Fisher has worked in tech M&A for 14 years, so he’s seen his shares of ups and downs.

“I’ve seen lots of different environments working here [at PwC],” Fisher tells peHUB. “We’re very busy and growing, and I don’t see that ending any time soon.”

He adds that “all the drivers are still there for robust market, and I don’t think we’re back in early 2009.”

M&A activity took a big hit in the first half of 2009 after the global financial meltdown in 2008. At that time (March 2009), the Nasdaq hit an intraday low of 1,265.52, which was nearly 55% below its bull-market high in October 2007. In contrast, despite the wild swings in today’s market over the past few weeks, the Nasdaq closed at 2,446.06 today, down about 15% from its 52-week high of 2,887.75.

“I think market volatility can influence overall valuations and those changes can have the effect of killing deals, but I just don’t think a 15% decline in the Nasdaq will have that kind of impact,” Fisher says.

PricewaterhouseCoopers hasn’t changed its outlook from mid-2011, when it said it expected “U.S. M&A activity to continue to pick up steadily through the balance of 2011.”

“The fundamental drivers aren’t changing,” Fisher says, pointing to three key factors that he sees as drivers for M&A activity: (1) convergence of computing, communications and entertainment products and services on consumer devices, such as smart phones; (2) consolidation of hardware, software services providers for the enterprise; and (3) cloud computing, which is impacting the business models of enterprise and some consumer tech companies and driving them to purchase cloud companies.

It’s true that some of PwC’s clients are now proceeding with more caution and doing more diligence on deals, but “those three factors continue to drive a substantial portion of activity,” Fisher says.

He adds that he is hard pressed to think of a particular category in tech that might see a dramatic decline in M&A because of market volatility.

Even if a company wanted to pull back, external market forces might force it to react. “These very large companies are doing very large transactions,” Fisher says. “They tend to create responses among competitors and suppliers — they have a ripple effect across industry.”

The third quarter has not yet closed, but VC-backed M&A is already ahead of where it was in the first three-quarters of last year, according to Thomson Reuters (publisher of peHUB). The disclosed value of completed VC-backed deals from Jan. 1 to Aug. 22 is $16.6 billion, up from $12.4 billion in the first full nine months of 2010 and $4.5 billion in the first nine months of 2009.

The number of transactions, on the other hand, is running behind last year. For the first three quarters of 2010, 334 VC-backed deals were done, up from 199 in the same period a year earlier, according to Thomson Reuters. So far this year, 259 VC-backed deals have closed. It’s hard to draw any conclusion from that, since there could be a number of announced deals in the pipeline that will officially close before Q3 ends. As of Q2, the number of VC-backed M&A deals (211) wasn’t too far off the first half of 2010 (when 221 VC-backed deals closed), which was up substantially from the first half of 2009 (when 130 deals that got done).

The following slideshow shows the 10 largest VC-backed acquisitions that have officially closed so far in Q3. All the data are from Thomson Reuters.