Nvidia declined more than five percent over the past week while AMD fell 12 percent in that time period.

Nvidia’s decline was because of a negative Citron Research report in which Andrew Left suggested that people should flog off their Nvidia shares and buy Google.

Left said that Nvidia was getting competition coming from Intel, Google and Xilinx in the data centre markets and the likelihood of slowing growth in its gaming graphics card business.

Wells Fargo agreed: "We think that Nvidia has done very well in establishing itself as the dominant provider of standalone accelerator solutions for data center, but believe that this is already reflected in Nvidia's stock value,"

Wells Fargo analyst David Wong wrote: "Over time we think additional providers of standalone accelerators might emerge, helping to drive growth in the standalone processor market but reducing Nvidia's market share in this market."

Goldman Sachs told investors to sell AMD shares, questioning whether the recent cryptocurrency-driven demand for the company's graphics cards will last.

Goldman analyst Toshiya Hari wrote that the RX 570 and RX 580 graphics cards are sold out at numerous retail websites including NewEgg and Microcenter. "But while this dynamic may provide near-term upside to fundamentals, we believe [cryptocurrency mining] is unlikely to become a sustainable driver of EPS."

An AMD spokesperson responded to the Goldman report saying:

"When we outlined our growth strategy at our financial analyst day earlier this quarter we didn't highlight the cryptocurrency market as one of the drivers of growth for the business."