Nvidia's stock is down and AMD is up. The culprit may be Arista.

Shares of Nvidia and Advanced Micro Devices moved in opposite directions on Friday, after the CEO of Arista Networks told investors that her company is seeing some deployment shifting to AMD.Nvidia's stock fell almost 3%, while AMD gained close to 1%."A year ago, it was pretty much 99% Nvidia, right?" Ullal said on Arista's earnings call late Thursday, when asked by an analyst about the company's work with AMD. "Today, when we look at our deployments, we see about 20%, maybe a little more, 20% to 25%, where ...