SANTA CLARA, California/TOKYO (Reuters) -Japanese technology investor SoftBank Group is accelerating its move into chip technology companies with the $6.5 billion purchase of Ampere Computing, a U.S. chip startup founded by the former president of Intel.

The all-cash deal announced on Wednesday comes as SoftBank steps up its investment in the infrastructure needed to power artificial intelligence, which founder Masayoshi Son has latched on to as his latest grand bet on a transformative technology.

It follows a series of multi-billion dollar investments announced in recent months, including in ChatGPT operator OpenAI, the Stargate project to build AI data center infrastructure in the U.S. and Cristal, a joint venture with OpenAI to develop AI services in Japan for corporate customers.

Ampere makes data center central processing unit (CPU) chips based on a computing architecture from SoftBank's majority-owned Arm Holdings that are used by firms such as Oracle in their cloud computing infrastructure.

As part of the deal, Ampere's biggest investors, Oracle and Carlyle Group ( CG ), will sell their respective positions in the company, SoftBank said.

Son said in a statement that the future of "artificial super intelligence" would require breakthrough computing power.

"Ampere's expertise in semiconductors and high-performance computing will help accelerate this vision, and deepens our commitment to AI innovation in the United States," he said.

Founded in 2018 by Intel veteran Renee James, Ampere built CPUs with its own custom computing core technology, a step usually only taken by much larger firms like Apple or Qualcomm.

Arm ultimately became a competitor as it sought to work directly with customers such as Microsoft and Google to help them build their own custom Arm-based CPUs.

Google had adopted Ampere's chips, but a year later after Google worked with Arm to develop its own "Axon" CPU, a Google executive told Reuters it would not be deploying more Ampere chips.

Under SoftBank's ownership, Ampere will be a stable mate of Arm in the Japanese conglomerate's growing collection of chip technology companies that are boosting their focus on AI.

SoftBank's Son made his name and fortune on high conviction bets on new technologies, such as e-commerce and mobile internet, but his foray into AI has come at a time of sky-high valuations and his investment record is patchy.

Shared office provider WeWork went into administration after SoftBank poured billions of dollars into it, while the portfolio of technology startups held by the Japanese company's Vision Fund investment vehicles has plummeted in value since 2022.

(Reporting by Stephen Nellis in Santa Clara, California, Anton Bridge in Tokyo and Harshita Meenaktshi in Bengaluru; Editing by Alan Barona and Jamie Freed)