This might be a pretty simple question, but I am wondering if neuromorphic computers using non Von Neumann architectures such as the IBM TrueNorth chip are still considered digital computers.

I have heard that some neuromorphic computers (don't remember which) use analog measurements rather than calculations when computing, but I believe that the interfaces are mostly digital. I am wondering if it affects the categorization of the class of computers.


I'm no expert, but on this page http://research.ibm.com/cognitive-computing/neurosynaptic-chips.shtml there is an article linked:


"Demonstrated a key building block of a novel architecture, namely, a neurosynaptic core, with 256 digital integrate-and-fire neurons and a 1024×256 bit SRAM crossbar memory for synapses using IBM 45nm SOI process."

It looks like they are composed of digital logic.

From the abstract of that linked article:

Abstract—The grand challenge of neuromorphic computation is to develop a flexible brain-like architecture capable of a wide array of real-time applications, while striving towards the ultra-low power consumption and compact size of the human brain—within the constraints of existing silicon and post-silicon technologies. To this end, we fabricated a key building block of a modular neuromorphic architecture, a neurosynaptic core, with 256 digital integrate-and-fire neurons and a 1024×256 bit SRAM crossbar memory for synapses using IBM’s 45nm SOI process. Our fully digital implementation is able to leverage favorable CMOS scaling trends, while ensuring one-to-one correspondence between hardware and software. In contrast to a conventional von Neumann architecture, our core tightly integrates computation (neurons) alongside memory (synapses), which allows us to implement efficient fan-out (communication) in a naturally parallel and event-driven manner, leading to ultra-low active power consumption of 45pJ/spike. The core is fully configurable in terms of neuron parameters, axon types, and synapse states and is thus amenable to a wide range of applications. As an example, we trained a restricted Boltzmann machine offline to perform a visual digit recognition task, and mapped the learned weights to our chip.


The citation on the wikipedia page leads to this article in spectrum. They also present multiple chips at the bottom, some of which are labelled as being purely digital (IBM TrueNorth, SpiNNaker), some as hybrid (Neurogrid, HRL neuromorphic chip, HiCANN).

I'm also not an expert as to what can be named how, but the architecture of a computer should have no impact on whether it can be called a digital computer (there are other architectures around, like Harvard architecture).

So only the real implementation of a chip would matter to me and as it stands the IBM TrueNorth is a pure digital chip, so yes it's a digital computer. The other chips mentioned are using analog circuits for calculation and digital circuits for communication(1), and I'd say they don't qualify as digital computers any longer.


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