(New York) The stock of British microprocessor designer Arm gained nearly 20% on Thursday shortly after the start of its trading, compared to the price set on Wednesday, a solid start for the largest IPO in almost two years.

After starting its run at $56.10 (10%), the stock hit $60 around 12:30 p.m. ET, 17% higher than Arm’s $51 on Wednesday.

During Thursday’s price, which is likely to evolve further during the rest of the session, the British flagship was valued at 61.5 billion dollars, and 64 including the securities allocated to employees and managers.

The first day of trading often sets the tone for a company’s stock market performance during its first months on the market.

“We are delighted to go public today, happy for all our employees, our partners and our developers,” CEO Rene Haas said on CNBC.

This is a return to the stock market for Arm, which already made a first gallop on the stock market from 1998 to 2016, before its takeover by the Japanese investment company SoftBank Group, for $32 billion.

At the origin of this reintroduction, SoftBank chose to only dispose of approximately 10% of the capital, and will recover, at least, 4.8 billion dollars, and up to 5.2 billion in the event of exercise the over-allotment option, which allows intermediary banks to acquire additional securities.

As for the balance, the boss and founder of SoftBank, Masayoshi Son, indicated Thursday on CNBC that he intended to keep it. “I want to keep as much as possible, for as long as possible,” he said.

The fact that SoftBank remains the owner of around 90% of the shares could make Arm a volatile stock on the stock market, where it is more difficult to find a seller or a buyer when the float (number of shares in circulation) is limited.

After considering a listing in London, the British Arm preferred New York, a snub for the British financial center.