University of Stanford Designs a Proof-of-concept Processor using Carbon Nanotubes

“People have been talking about a new era of carbon nanotube electronics moving beyond silicon. But there have been few demonstrations of complete digital systems using this exciting technology. Here is the proof.”

Stanford Professor Subhasish Mitra in a release from Stanford University

Computer Processor design just took a leap forward into the future with the development of a proof-of-concept Processor based on CNT (Carbon Nanotubes) as described in the article “First carbon nanotube computer to help extend Moore's Law?”, published September 25, 2013 4:19 PM PDT by Eric Mack, CNET News. For those with little trust in CNET News, here’s the news straight from the Horses Mouth in the article A first: Stanford engineers build basic computer using carbon nanotubes, September 26, 2013, by Tom Abate, Stanford University.

The leap forward was made on Wednesday September 25^th 2013 by the Stanford professors

Subhasish Mitra and H.S. Philip Wong at Stanford University. They had help with designing this first 800nm CNT Processor, dubbed “Cedric”, from a few Doctoral Students using the limited equipment available to them at Stanford to make a CNT Processor:

1.      Max M. Shulaker,

2.      Gage Hills

3.      Nishant Patil        

4.      Hai Wei    

5.      Hong-Yu Chen

You can scope it out in the Nature Journal Magazine article “Carbon nanotube computer”, Received 12 May 2013 Accepted 24 July 2013 by H.-S. Philip Wong & Subhasish Mitra et al, Nature Journal.

           

This first Computer based on CNT’s had only 178 transistors, the basic building blocks of most Processors. At that count, it had the computing power of a typical Intel 4004 Processor. In the process of making the CNT Processor, they’ve solved several problems as relates to growing CNT and fabricating them into a Processor.

To their credit, the Stanford Team didn’t have access to the Industrial Fabrication techniques of companies like Intel or AMD (Advance Micro Devices). They also had to content with the imperfect nature of these thinner than a human hair CNT that are made up of Carbon Cages that since January 2013 can be fabricated cheaply on demand and some of which once configured into a transistor, refuse to switch on and off properly.

Imperfection-immune design – A self correcting CNT Processor

As it relates to the manipulation of the CNT, they had to overcome several problems, the main two being misaligned CNT’s and Metallic CNT’s. This as the team aimed to design an Industrial process to manufacture CNT’s that could be scaled up from the Lab to Fab, to quote Professor

Subhasish Mitra: “We needed a way to design circuits without having to look for imperfections or even know where they were”.

Their design philosophy, called “imperfection-immune design” meant building the CNT Processor to function even if it had physical imperfections due to misaligned CNT’s and Metallic CNT’s a fraction of which appear whenever CNT’s are fabricated. A complex algorithm was used to help the Processor cope with the misalignments in the CNT’s used to produce the transistor logic gates and the traces used to carry current in the Processor. 

The problem of Metallic CNT’s was solved simply by burning them off. Since the Metallic CNT, the ones that conducted electrons instead of acting like semiconductor material that could be turned on and off like switches was in the minority, they simply turned off the power to the good transistors and powered up the entire circuit. The semiconductor material didn’t carry current but the metallic gates did, literally burned away in puffs of Carbon Dioxide as the heat helped to oxidized them.

Using this “imperfection-immune design” technique and the limited fabrication facilities is what gave birth to the 178 transistors, suggesting more was possible with Industrial scale facilities. The Processor basically possesses the same power as an Intel 4004. Running a basic operation system, most likely written in Linux, the CNT Processor is able to do the following:

1.      Counting

2.      Number sorting

3.      Running MIPS a commercial instruction set developed in the early 1980s by then Stanford engineering professor and now university President John Hennessy.

This design technique is an amazing achievement for a Processor built using CNT as stated in “A first: Stanford engineers build computer using carbon nanotube technology”, Sept 25, 2013, Phys.org, which clearly paves the way for CNT’s being built and tested at a commercial level, to quote Sankar Basu, a program director at the National Science Foundation: “This 'imperfections-immune design' (technique) makes this discovery truly exemplary”.

Advantages of CNT Processors – Room Temperature Supercomputers

But the advantages of using CNT’s are obvious. Made up of a honeycomb Network of Carbon atoms, they are superconductors at room temperature due to the uniform pathways that the CNT creates for electron flow. Thus current flows with almost zero resistance at room temperature and maintain their performance even at elevated temperatures.

Because of their thickness, which is significantly smaller than a human hair, they dissipate less energy and thus require smaller current to work, Building Semiconductor transistors with time, though, is a challenge as their superconducting capabilities means that they have to be specially fabricated so as to reduce the formation of metallic CNT’s and are mainly semiconductors in their electrical behavior.

Processors based on CNT have the capability to achieve clock speeds as high as 10GHz, double that of the 5GHz FX-9000 from AMD as reported in my Geezam blog article entitled “AMD unveils 5GHz and 4.7Ghz 8-Core Processor at E3 2013 in Apple’s Mac Pro Dogfight for Top Gun in High End Multi-Core PC Gaming” but with much cooler operating temperatures and with more stable performance.

Best of all, CNT Based Processors can already interface directly with electronics built for silicon Chips, making them an easy slot in replacement without the need to change the architecture of computers as they exist today. Throw in the fact that merely adding strands of CNT’s to any compound makes it structurally stronger, they are a perfect material for making Processors and a replacement for using Silicon, the standard for years in Processor Fabrication.

That is, if you can grow them cheaply and uniformly in a streamlined industrial process to make Processors. You can scope out more videos on YouTube on Carbon Nanotubes

More options to expand Moore’s Law – Optical, Quantum, Neural Net and now CNT

This development bears watching. Along with Optical Computers, Quantum Computers as described in my blog article entitled “Harvard and Massachusetts Institute of Technology create Molecules from Photons - The Force is Strong as Lightsabers, Optical Quantum Computers and Light Crystals are Possible” and Neural Net Computers that mimic the function of the brain by using Multi-core Processor Networks, CNT’s present yet another piece of technology to keep Moore’s Law moving forward.

It’ll take some time to reduce the size of the Processor down to the equivalent in the 24nm scale of the Intel and AMD Processor Fabrication World, as the fabrication scale, again limited by the equiptment available to the Scientists, was 800nm. This first CNT Processor, dubbed “Cedric”, has a long way to go before it’s at that stage ready to slot into a ZIF socket to replace a Silicon based Processor.

This may take years to achieve but as a first lays the groundwork for their practical fabrication by 2015 the earliest to quote Supratik Guha, director of physical sciences for IBM's Thomas J. Watson Research Center and a world leader in CNT research: “These are initial necessary steps in taking carbon nanotubes from the chemistry lab to a real environment”.

The first devices that’ll benefit when Stanford gets access to industrial equiptment and can make an entire Processor out of CNT will be mostly mobile computing devices i.e. Tablets and smartphones. Servers and Workstations will benefit next especially form the fact that their operation is more stable at lower temperatures and can provide higher speeds even while maintaining higher processing speeds.