MIT and ADI have built a 16-bit processor using CNTs.

10 million CNTs were used to form 14,702 CMOS CNT field-effect transistors (CNTFETs), arranged in 3,762 digital logic blocks, that together operated as a 16-bit processor.

The chip can fetch 32-bit instructions from memory, has a RISC-V register file, and can read and write 16-bit data from and to RAM. 

The peculiar characteristics of CNTs that have stopped the technology being useful as an IC substrate were addressed by DREAM, RINSE and MIXED.

RINSE (removal of incubated nanotubes through selective exfoliation), MIXED (metal interface engineering crossed with electrostatic doping) and DREAM (designing resiliency against metallic CNTs).

“My favourite part of being a part of this project is that it brings together researchers with expertise across a wide range of backgrounds, including material synthesis, physical fabrication, circuit design, computer architecture, and applications,” says MIT Prof Max Shulaker, “without innovations and support from the team in all of these areas together, it wouldn’t have been possible to demonstrate the modern microprocessor built entirely out of carbon nanotube field-effect transistors.”

“There are limits to silicon,” adds Shulaker, “if we want to continue to have gains in computing, carbon nanotubes represent one of the most promising ways to overcome those limits.”