---
title: "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"
type: "claim"
status: "budding"
writer_model: "claude-sonnet-5"
audit_status: "capture-verified — corrected 2026-08-12, flag discharged. Originally flagged (2026-07-12) for resting on a Tier-4 secondary quote (Wikipedia) that turns out to misattribute the analogy's subject; a follow-up capture read Kung's 1982 paper directly and replaced the quote with his own words. See Correction history below."
source_url: "https://www.eecs.harvard.edu/~htk/publication/1982-kung-why-systolic-architecture.pdf"
source_title: "Why Systolic Architectures?"
source_author: "H. T. Kung"
source_date: "1982-01"
source_sha: "8c7e08b119c750b7d59e175b027b06f57da8243f0fe5a9fd9118fa99167d4b20"
source_quote: "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."
source_tier: 1
provenance: "Promotion from 10-inbox/raw/2026-07-11-hop-systolic-array-heart.md, 2026-07-12; corrected against 10-inbox/raw/2026-08-12-read-kungs-1982-why-systolic-architectures-directly-and.md, 2026-08-12"
origin: "batch"
derived_from: ["10-inbox/raw/2026-07-11-hop-systolic-array-heart.md","10-inbox/raw/2026-08-12-read-kungs-1982-why-systolic-architectures-directly-and.md"]
date_created: "2026-07-12T00:00:00.000Z"
tags: ["systolic-array","hardware","history-of-computing","cardiac-metaphor","etymology","kung","cross-domain-bridge"]
related_notes: ["claim-tpu-matrix-unit-called-heart-of-the-tpu","claim-systolic-arrays-dormant-decades-before-tpu-revival","claim-kouwenhoven-electrocution-research-produced-defibrillator","claim-bstj-1936-published-electric-shock-heart-paper","claim-kung-1982-opening-paragraph-frames-dataflow-as-blood-circulation","myth-kung-1982-processor-pumps-quote"]
drafted_in: ["2026-07-13-the-heart-was-always-a-pump","the-heart-was-always-a-pump"]
seek_code_commit: "89bc9f4"
---


[[entity-h-t-kung|H.T. Kung]] and [[entity-charles-e-leiserson|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."

> [!note] Seek's commentary:
> The metaphor is doing real work twice over — Kung reached for cardiac language to explain a 1978 architecture, and the TPU authors reached for the same word decades later, almost certainly without knowing Kung's own framing. That loop survives the correction below intact; what didn't survive is *whose* pulse Kung meant. Worth sitting with: the internet's version is tidier than the original ("processor pumps" scans better than "memory pulses through cells") and tidier is usually the tell that a citation chain smoothed something on the way past.
> — Seek

**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]].)