**5.3 IBM's TrueNorth chip**

In 2014, IBM released the neuromorphic CMOS integrated circuit known as TrueNorth. With 4096 cores and 256 programmable simulated neurons per core for a

#### **Figure 4.** *Intel uses 64 Loihi research chips in its neuromorphic system called Pohoiki Beach [30].*

total of just over a million neurons, it is a manycore processor network on a chip. The 256 programmable "synapses" that connect each neuron serve to transmit impulses between them. Thus, there are little over 268 million programmable synapses overall. It has 5.4 billion fundamental transistors.

TrueNorth avoids the von Neumann-architecture bottleneck and is extremely energy efficient, with IBM claiming a power consumption of 70 milliwatts and a power density that is 1/10,000th of conventional microprocessors. Memory, computation, and communication are handled in each of the 4096 neurosynaptic cores [31]. The SyNAPSE chip operates at lower temperatures and power consumption because it only uses the power required for computing. Skyrmions have been proposed as models of the synapse on a chip [32, 33].

The neurons are emulated using a Linear-Leak Integrate-and-Fire (LLIF) model, a simplification of the leaky integrate-and-fire model [34]. IBM claims that it lacks a clock [35] and only uses unary numbers, counting up to a maximum of 19 bits to perform computations [34, 36]. The said cores are event-driven by using both a synchronous logic and are interconnected through an asynchronous packet-switched mesh network on chip (NOC).

In order to programme and use TrueNorth, IBM has created an entirely new environment. It featured libraries, a simulator, a fresh programming language, and even an integrated programming environment. Due to the substantial concerns of vendor lock-in and other negative effects, this absence of backward compatibility with any prior technology (such as C++ compilers) may preclude it from becoming commercialization in the future (**Figure 5**) [35].

### **5.4 Human brain project**

The European Union funded Human Brain Project (HBP), a 10-year endeavour that started in 2013, aims to better understand the brain through research in six areas, including neuromorphic computing. SpiNNaker and BrainScaleS are two significant neuromorphic university initiatives that were inspired by the HBP. The largest neuromorphic supercomputer in existence at the time, the million-core SpiNNaker system, was released in 2018; The University of Manchester plans to expand it up in the future to model one million neurons.

**Figure 5.** *Board with 16 TrueNorth chips.*
