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Equation 4 · Part 7 · Comparing the Main Approaches to Post-CMOS, Neuromorphic, Photonic, and Quantum AI Compute

subscript

Eop=Ecore+Eperiphery+EI/O,E_{\text{op}} = E_{\text{core}} + E_{\text{periphery}} + E_{\text{I/O}},
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

The physical limitation keeping analog in-memory compute confined to inference on weights that rarely change is the flip side of its core trick: a conductance that can be read out to represent a weight can also drift over time, and writing a new one wears the device in a way reading does not, so retraining costs more, in time and device lifetime, than in a design where weights sit in ordinary digital memory. A simple accounting for why raw operations-per-watt numbers are not directly comparable across any of the four approaches in this piece is worth writing out once: Eop=Ecore+Eperiphery+EI/OE_{\text{op}} = E_{\text{core}} + E_{\text{periphery}} + E_{\text{I/O}}. where EcoreE_{\text{core}} is the energy of the operation itself — the multiply-accumulate, the interference…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →

Sources cited in the article section

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