Riot Blockchain (NASDAQ:RIOT) stock dips 4.9% in premarket trading after the bitcoin miner shut down most of its huge mining operation in Texas as cold and ice move into the state. The stock may also be affected by Bitcoin (BTC-USD), falling 5.9% to $36.5K. On Tuesday morning, Riot (RIOT) voluntarily started to power down bitcoin mining servers at the Whinstone facility, and by the next day had cut its energy use by ~98%, a company spokesperson told Bloomberg News via email. On Monday, Riot's CEO and Whinstone's CEO told Governor Greg Abbot's office that they were planning to cut back on power use at Whinstone, the state's largest bitcoin miner, as the winter storm approached. The storm will be the first big test of state's power grid and its operator Electricity Reliability Council of Texas (Ercot) since last February's ice storm caused massive power outages across the state. "Whinstone began taking proactive measures to