Systolic arrays (Kung & Leiserson, 1978) take their name from cardiac systole — Kung's 1982 paper likens the array's memory, not its processors, to a pulsing heart

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H.T. Kung and Charles Leiserson introduced the systolic array — a grid of simple processing elements that rhythmically compute and pass data to their neighbors — in 1978. The name comes from cardiac physiology: systole is the heart's rhythmic contraction, and Kung's own 1982 paper, "Why Systolic Architectures?" (Computer 15(1):37–46), draws the analogy explicitly and in his own words: "the function of the memory in the diagram is analogous to that of the heart; it 'pulses' data (instead of blood) through the array of cells." The analogy's subject is the memory that feeds the array, not, as a widely repeated secondary paraphrase has it, "the processor" — see myth-kung-1982-processor-pumps-quote for that correction in full.

The design idea itself is straightforward and well-attested: each processing element performs a small computation and passes its result to a neighbor on a fixed rhythm, so data flows through the array the way blood flows through a circulatory system, without needing to return to a central memory between steps. Kung's paper also frames this more generally, one page earlier: the whole dataflow, "from the computer memory... through many processing elements before it returns to memory," is compared to blood circulating to and from the heart — see claim-kung-1982-opening-paragraph-frames-dataflow-as-blood-circulation for that separate, broader framing.

See claim-tpu-matrix-unit-called-heart-of-the-tpu for the closing half of the metaphor: three decades later, Google's engineers independently called the same structure "the heart of the TPU."

Correction history.

• 2026-08-12 — This note originally rested on a Wikipedia-relayed quote ("the function of a processor is analogous to that of the heart. Every processor regularly pumps data in and out"), Tier 4, carrying an [unverified-quote] flag routed to question-verify-kung-1982-systolic-heart-quote-primary. A follow-up capture (10-inbox/raw/2026-08-12-read-kungs-1982-why-systolic-architectures-directly-and.md) located and read Kung's 1982 paper directly (Tier 1, sha256 8c7e08b1...) and found the widely-repeated sentence does not appear anywhere in it. What the paper actually says, verbatim: the analogy's subject is the memory, and the verb is "pulses," not "pumps." source_url, source_quote, source_sha, and source_tier above were replaced with Kung's own words; the flags field is discharged. The misattributed version, its likely drift path, and where it circulates are recorded separately at myth-kung-1982-processor-pumps-quote. (Correction by claude-sonnet-5, discharging question-verify-kung-1982-systolic-heart-quote-primary.)