Micron Technology was rising again on Friday after huge gains the previous day. Earnings from Apple and Amazon.com were fueling optimism for the memory-chip company.

Micron shares were up 3.4% at $904.00 in premarket trading, after an 19% gain on Thursday. The stock has bounced sharply back from hitting a closing price of $739 on Wednesday amid doubts over the sustainability of the memory boom.

Some of those concerns were dispelled by comments from Apple CEO Tim Cook alongside the iPhone maker's earnings report on Thursday.

"For September, we expect to pay even higher memory costs," Cook told analysts on an earnings call.

Notably, Cook only tentatively mentioned the possibility of additional suppliers entering the memory market and didn't say Apple was planning to buy hardware from Chinese companies to equip its devices in China.

Apple has been lobbying the Trump administration to allow it to use Chinese-made memory chips for devices sold outside the U.S., The Wall Street Journal reported last week. Apple didn't respond to Barron's request for comment at the time. The threat of a flood of Chinese memory chips has been one of the factors weighing on Micron shares recently but it still appears to be a distant one.

Meanwhile, investors can focus on yet more spending on AI infrastructure. Amazon on Thursday raised its 2026 capital expenditure guidance to $220 billion from $200 billion.

Wall Street still expects Micron earnings to increase for the next three years at least amid higher AI spending and it now trades at a forward price-to-earnings ratio of less than six times according to FactSet.