Google (GOOG) said Thursday afternoon Schmidt will step aside after 10 years as chief executive. He’ll be replaced by co-founder Larry Page. Schmidt will stay on as chairman.*

Schmidt said in Google’s press release that the change will “create clearer responsibility and accountability at the top of the company.”

But that’s not all: the shake-up will also give Schmidt a chance to cash in the increasingly lucrative Google chips he has mostly hung onto for the past decade.

Schmidt holds 9.2 million Google shares that at current prices are worth almost $5.8 billion. Google said in a regulatory filing that Schmidt plans to sell 6% of that stake over the next year under a preplanned trading arrangement he filed last month with the Securities and Exchange Commission.

The company said that if he completes the trading plan as laid out, he would sell 534,000 shares, taking his ownership of Google down to 2.7% from the current 3.1% and reducing his voting stake to 9.1% from 9.6%. Schmidt hasn’t sold any Google shares since 2007 — unlike co-founders Page and Sergey Brin, each of whom said last year they would sell 5 million shares.

Schmidt would clear $334 million on his stock sale were it all to take place at Thursday’s prices.

Of course, it’s not that he wants the money or anything.

“Using this trading plan, Eric can diversify his investment portfolio and can spread stock trades out over a period of one year to reduce market impact,” Google said. “Because this trading plan was established well in advance of a trade, it also helps avoid concerns about whether Eric had material, non-public information when he made a decision to sell his stock.”

Yes, insider selling is all about diversifying portfolios, reducing market impact and avoiding concerns. No question.

In any case, the shares Schmidt plans to sell are all Class A shares – the ones that trade freely in the markets and carry a single vote for each share.

Schmidt, Page and Brin together own all of a super-voting class of stock, designated Class B, that carries 10 votes for each share. That arrangement will allow them to keep voting control of the company even if Google issues millions more shares in acquisitions or to compensate workers.

All three have all been making $1 a year in salary, though Schmidt also received $3,558 in holiday bonuses in 2007 and 2009. He also got around $411,000 a year over the past three years in company-paid security and private-plane benefits.

Google didn’t say whether he’d continue to receive his princely salary as non-executive chairman, but let’s face it — he won’t need that dollar anyway.

*Update: Google is calling Schmidt’s new job “executive chairman.”  Initially I incorrectly described it as nonexecutive chairman. I have also added background on planned stock sales by Page and Brin.