During California's Gold Rush, it was often the sellers of pickaxes and shovels who made the most money. In the frenzy to get rich quick from cryptocurrencies, some investors are calling computer chipmakers the modern-day equivalent. From a report: Shares of Nvidia and Advanced Micro Devices have gained at least 14 percent since the beginning of June, spurred in part by about a 10-fold boom from April to June in a market, known as ethereum, for a currency that can be used to buy computing power over the internet. What's the link between ethereum and these Silicon Valley chipmakers? It lies in the really powerful graphics processors, designed to make computer games more realistic, that are also needed to gain access to encrypted digital currencies. Nvidia and AMD have rallied in the last month and a half even as investors have ignored chip stocks leaving the benchmark Philadelphia Stock Exchange Semiconductor Index up about 1 percent. Nvidia has gained 14 percent and AMD rallied 27 percent. While some of that has come from optimism around new products for other markets, analysts are projecting that sales related to cryptocurrencies will result in a spike in revenue for both companies. Even so, investors shouldn't bank on a lasting impact from the cryptocurrency boom, said Stacy Rasgon, an analyst at Sanford C. Bernstein & Co. "This has happened before," Rasgon said. "It lasted about a quarter." [...] Like bitcoin, ethereum is an attempt by an online community to create an economy that doesn't rely on government-backed currencies. Unlike bitcoin, it's focused solely on offering decentralized computing and storage services. Those seeking to use these services -- and speculators looking for a quick profit by creating and then selling ether -- have seized on graphics cards, which excel at performing multiple simple calculations in parallel, as a faster way to claim the blocks of code that act as the currency of the ethereum market. Demand from ethereum miners has created temporary shortages of some of the graphics cards, according to analysts, who cite sold-out products at online retailers. Estimates of additional sales from this demand run as high as $875 million, according to RBC Capital Markets analyst Mitch Steves. That would roughly equal AMD's total sales from graphics chips last year, or half of Nvidia's quarterly sales of those components. But Steves and other analysts are also quick to warn that the market opportunity could fizzle out.