Advanced Micro Devices Inc. AMD, +1.36% stock fell 6.5% in the extended session Thursday after Nvidia Corp. NVDA, +1.93% released earnings that included graphics processing unit inventory issues. On its conference call late Thursday, Nvidia said that its GPU inventories were building up, creating a backlog of unsold cards and chips. The inventory issue was also affecting competitors, Nvidia said. "I think the channel has more than 12 weeks of inventory between us and the other brand," Nvidia Chief Executive Jensen Huang said in the conference call Thursday. "The amount of inventory is not just us it's also the other brands. And our ability to see the other brand's inventory is just much harder. We try our best to estimate it but obviously we didn't estimate it well enough. And so the answer to your question is yes I think there's about, from our perspective, about 12 weeks of our inventory to sell-through at this point." An AMD spokesman said in an email Thursday that the company had already disclosed crypto weakness in its most recent earnings report, and that Nvidia was just "reaffirming what we have already called out." Nvidia stock has fallen 17% in the extended session and closed up 2.6% to $202.39 in regular trading. The S&P 500 index SPX, +0.14% closed up 1.1% Thursday.