That's 1,000,000,000 cycles per second. The basic problem lies in how small an electrical circuit line can be made. Microchips are produced using a technique called photolithography, a variation of the method used to produce art prints. A pure silicon glass wafer is coated with a photosensitive chemical, just like the film in a camera. A source of light, typically from a laser is focused through a mask that contains the image of the chip design onto the surface of the silicon wafer.
Chemicals then etch away all but the chips circuit line patterns.
The process is repeated producing all the layers of circuits that are interconnected forming the microchip. Chip manufacturers using the latest technology can print circuit lines as small as 0.1 microns, about one-thousandth the diameter of a human hair. The process, called deep ultraviolet photolithography was set to run out of steam in 2004 or 2005 even after predicted innovations to the present process were employed. The dead-end is caused by the wavelength of the laser light used. To get smaller circuits the light used would have to be of a smaller wavelength in the region designated as extreme ultraviolet.