A smartphone with a displayed NVIDIA logo is placed on a computer motherboard in this illustration. Image Credit: Reuters

Nvidia Corp.'s run as the world's biggest company didn't last long.

Shares of the semiconductor giant have tumbled on back-to-back days, dropping more than 7 per cent, after rallying earlier in the week and pushing its valuation to $3.3 trillion, just above Microsoft Corp. and Apple Inc. Traders said there weren't any fundamental reasons behind the two-day selloff but it does, if nothing else, underscore how big the company had become after almost tripling in value over the past year.

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Given the three megacaps have jockeyed all month for the pole position, Nvidia, of course, could reclaim the top spot soon enough after shedding more than $200 billion in market value in two days.

"Nothing has gone wrong at Nvidia, which reached the number one spot earlier this week," said Russ Mould, investment director at AJ Bell. "It's just the usual fluctuations in the stock market which, with such large companies, can wipe or add hundreds of millions or even billions of dollars to their market value."

The drop also comes amid broader market retreat as options expire in a so-called triple-witching session. As the contracts disappear, investors will adjust their positions, adding a burst of volume capable of swinging individual holdings.