Potentially the world’s biggest bitcoin mine is said to have signed up two top corporate customers, SBI Holdings and GMO.

The Japanese corporate giants will be renting mining capacity at the facility in Rockdale, Texas, recently put into construction by Whinstone Inc., according to Bloomberg sources. The firms are to begin mining “within coming months,” the report says, adding that the firms involved would not comment when asked.

As CoinDesk reported in November, when the facility gets up and running it will likely be the biggest bitcoin mine in the world, starting at 300 megawatts and expanding to 1 gigawatt by the end of 2020.

That puts the rival mine being built by Bitmain – also in Rockdale and touted as the biggest in the world – in the shade. That’s planned to start at a capacity of 25-50 MW and possibly expand to 300 MW.

Internet giant GMO was also said to have been involved in setting up the Rockdale facility, as per CoinDesk’s earlier report. In November, Whinstone estimated the data center will cost $150 million to build and fit out. The initial 300 MW of power was expected to come online in the first quarter, with 1 GW planned to be achieved late in the year.