Jensen Huang outlined how difficult it was to build Nvidia.Sam Yeh/AFP/Getty ImagesNvidia's Jensen Huang explained just how tough it was to build the chipmaker into a world-beater.The CEO ticked off the knowledge and people required, and the competition and challenges he faced.Startup founders don't know what they're signing up for — and that's a good thing, Huang said.Starting Nvidia from scratch and growing it into a $3 trillion company took three decades and stretched Jensen Huang to his absolute limit."Building a company is insanely hard," the chipmaker's cofounder said in a video shown at "Acquired Live" last month and posted online this week."The number of things that you have to know.