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Equation 12 · Part 9 · How AI Memory Systems and the Bandwidth Wall Actually Work

subscript

MKV  =  2 n h d e b l,M_{\mathrm{KV}} \;=\; 2 \, n \, h \, d \, e \, b \, l ,
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

Hooper and colleagues, working on KV cache compression for very long contexts, state the resulting footprint precisely: for a model with n layers and h attention heads of dimension d , stored using e bytes per element, the KV cache size for batch size b and sequence length l is MKV  =  2 n h d e b lM_{\mathrm{KV}} \;=\; 2 \, n \, h \, d \, e \, b \, l . which grows linearly in both batch size and sequence length, with the leading factor of two accounting for storing both keys and values [ 9 ] . That single equation is the whole mechanism: nothing about it is a design choice an inference engineer can simply decline. Extend the conversation, and l grows; serve more requests at once, and b grows; either way MKVM_{\mathrm{KV}} grows with it, and Hooper…

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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 surrounding passage

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