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(rF/rB)5.5=(1.875)5.5≈32(r_F/r_B)^{5.5} = (1.875)^{5.5} \approx 32

Why this formula appears here

With rFr_F ≈\approx 3.0 and rBr_B ≈\approx 1.6 for DRAM bandwidth, (rFr_F/rBr_B)^{5.5} = (1.875)^{5.5} ≈\approx 32 : the ratio of peak arithmetic to memory bandwidth would be roughly 32 times higher in 2035 than in 2024 if the historical exponents hold exactly. Swap in interconnect bandwidth’s 1.4x rate and the same arithmetic gives (3.0/1.4)^{5.5} ≈\approx 66 . Neither number is a forecast; both are what the stated assumption implies, and the assumption — that both exponents stay fixed for eleven more years — is exactly the thing worth doubting. HBM4’s own arrival already shows one departure from smooth continuation: doubling per-stack bandwidth required doubling channel count as well as pin rate, and…

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rFr_F

Symbol r_F

rFr_F is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

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rBr_B

Symbol r_B

rBr_B is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

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How to interpret it

Its accuracy depends on the assumptions and range of use described in the article. Read it with the definitions, units, and assumptions supplied by the article.

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Published contexts (1)

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(rF/rB)5.5=(1.875)5.5≈32(r_F/r_B)^{5.5} = (1.875)^{5.5} \approx 32

Equation 4 · Semiconductors

AI Accelerator Architecture in 2035: Scenarios, Signals, and Falsifiable Predictions

This equation gives an approximation: it relates the quantities while allowing an approximation.

With rFr_F ≈\approx 3.0 and rBr_B ≈\approx 1.6 for DRAM bandwidth, (rFr_F/rBr_B)^{5.5} = (1.875)^{5.5} ≈\approx 32 : the ratio of peak arithmetic to memory bandwidth would be roughly 32 times higher in 2035 than in 2024 if the historical exponents hold exactly. Swap in interconnect bandwidth’s 1.4x rate and the same arithmetic gives (3.0/1.4)^{5.5} ≈\approx 66 . Neither number is a forecast; both are what the stated assumption implies, and the assumption — that both exponents stay fixed for eleven more years — is exactly the thing worth doubting. HBM4’s own arrival already shows one departure from smooth continuation: doubling per-stack bandwidth required doubling channel count as well as pin rate, and…

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