The Roundhill Memory ETF (DRAM) just hit $9.8 billion in assets under management in 43 days— the fastest pace ever for an exchange-traded fund, according to TMX VettaFi. Ahead of Thursday's milestone, the CEO of Roundhill Investments told CNBC's " ETF Edge " the rapid growth is tied to the limited number of companies involved in producing high-bandwidth memory or DRAM chips. They're considered integral to the artificial intelligence revolution. "Investors are waking up to the fact that the biggest bottleneck in the AI build-out is actually memory chips," Dave Mazza said Monday. "There's an incredible amount of supply and demand imbalance with memory which is one of the reasons why the stocks have been performing so well." Mazza notes just a small number of companies are involved in making high-bandwidth memory chips. "This is an area where memory has historically been incredibly cyclical. We've seen boom-and-bust cycles.…