The Japanese company said in a statement Wednesday that the impact of the deal on its finances and earnings is under review. SoftBank shares rose as much as 8% Wednesday morning in Tokyo.

Ampere was founded by former Intel Corp executive Renee James to pioneer the market for data centre processors based on Arm Holdings Plc technology.

James signed up high-profile customers and assembled a large engineering team with experience serving that lucrative segment of the semiconductor industry.

SoftBank is already the majority owner of Arm, whose technology is used across the electronics market and increasingly as the basis for server chips.

The Tokyo-based company also owns UK-based Graphcore Ltd, which SoftBank founder Masayoshi Son has said will help provide the technologies needed for artificial intelligence components.