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Equation 4 · Part 2 · Comparing the Main Approaches to Chiplets and Advanced Packaging

subscript

fbf_b
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

where fbf_b is the data rate carried by a single connection. The relationship is quadratic in pitch, not linear: halving the pitch alone — with no change to the per-connection data rate — quadruples the number of connections available in the same area, and therefore roughly quadruples aggregate bandwidth density. That is why the packaging industry has spent so much engineering effort on pitch specifically, rather than on pushing more current or a faster signal through the connections that already exist: geometry, not signalling rate, is the cheapest source of additional bandwidth once a joint is already short and direct.

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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.

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Sources cited in the article section

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