A new plastic processor for less than a penny a piece

For decades we have aspired to have a world in which all common objects, such as bandages and bottles, have a sort of integrated intelligence thanks to super cheap and inexpensive processors in terms of energy. With the surge in demands related to the world of IoT (Internet Of Things), some large companies have started to think about alternative solutions. This is the case of a group of researchers, who have found a way to create a plastic processor that can be mass-produced for less than a cent a dollar .

The research team thus presents a truly simple processor compared to today's standards (even in comparison to the simplest microcontrollers) but fully functional processor: Flexicore .

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A 4-bit plastic processor

The processors made by the team were made using the flexible semiconductor technology IGZO (Indium Gallium Zinc Oxide), which can be built on plastic and continue to function even if folded on itself with a radius of a few millimeters (therefore flexible). But while a reliable manufacturing process is a prerequisite, it was the design that made the difference.

So instead of adapting an existing architecture, the team started from scratch to create a project called Flexicore. With the aim of minimizing the number of logic gates necessary to build the processor, they arrived at a 4-bit architecture instead of 8, 16 or 32 bits, and this helped a lot. It also helped to separate the memory that stores the instructions from the memory that stores the data. Obviously, it was also necessary to reduce the number and complexity of the instructions that the processor is able to execute, in order to reduce the complexity of the control and execution part. From here it is understood that it is not simply a processor, but it is something more complex that includes both a CPU and memory, effectively making it a microcontroller in all respects.

Overall, we were able to simplify FlexiCore's design by adapting them to the needs of flexible applications, which tend to be computationally simple.

All of this resulted in a 5.6mm2 4-bit FlexiCore made up of just 2104 semiconductor devices (about the same number of transistors in a 1971 Intel 4004) compared to about 56,340 devices for PlasticARM :. This is an order of magnitude smaller than the smallest silicon microcontrollers in terms of gate count. The team also tried to produce an 8-bit processor but they got a lower yield and therefore less cost-effective.

In the future, the researchers will seek to optimize the microcontrollers in question for different processes and workloads . For example, one can think of specific and optimized architectures for different areas. Certainly, the production of such chips will lead to the integration of electronic components virtually everywhere. The research will be presented at the International Symposium on Computer Architecture in late June 2022.

What's wrong with silicon?

Why is the team pushing towards the use of this particular technology instead of the classic silicon, to which we are all used to and of which we have so much knowledge? The analysis made by the researchers suggests that silicon is not suitable for this task: compared to plastic, in fact, it is expensive and inflexible even if it is possible to obtain a great level of miniaturization .

Furthermore, there are problems related to the production of silicon chips. Current manufacturing processes allow for a very small circuit area, but it is still necessary to leave a relatively large amount of space around it so that the chip can be cut from the wafer in which it was printed. In the case of a simple processor like the Flexicore, there would be more space around the edge than the area containing the circuits . Additionally, space is required to insert enough I / O pads so that data and power can reach the chip. Suddenly, a large area of ​​silicon is needed, and this pushes the overall spend beyond the critical $ 0.1 threshold .

The article A new plastic processor for less than a cent a piece was written on: Tech CuE | Close-up Engineering .