🧠 中央处理器：电脑的“大脑”🧠 Central Processing Unit: the computer's brain

上一片里，小数终于会算了。可谁来干活？小电脑指指自己的脑袋：中央处理器 CPU，循环做三件事，不停不歇。 Last leaf, decimals finally learned to compute. But who does the work? The little computer points at its head: the CPU, looping through three jobs without rest.

第 1 步：取指→解码→执行，无限循环Step 1: Fetch → decode → execute, on loop

CPU 的工作像送快递：永远是拿单、看单、干活三步。The CPU works like a courier: always grab the order, read it, do it.

CPU 三步走：取指、解码、执行 — 取指去内存拿任务卡 3+5，解码看懂“原来是加法”，执行算出 8。一秒循环几十亿次，这就是冯诺依曼存下的老规矩。 Fetch grabs task card 3+5 from memory, decode reads “it's an addition”, execute gets 8. Billions of loops per second — the old von Neumann rule.

一秒几十亿次？这个速度怎么表示？Billions per second? How is that speed written?

第 2 步：主频是拍子，核心是双手Step 2: Clock is the beat, cores are hands

主频表盘：3.5GHz 每秒 35 亿次 — 主频 GHz 是节拍器：3.5GHz = 每秒 35 亿拍，一拍干一点活。核心数是双手：8 核能同时端 8 盘菜，多任务不打架。 Clock in GHz is the metronome: 3.5 GHz = 3.5 billion beats per second, one beat one bit of work. Cores are hands: 8 cores carry 8 dishes at once.

什么都自己干吗？遇到一千件同样的活呢？Does it do everything alone? What about a thousand identical jobs?

第 3 步：全能手请出大力士Step 3: The all-rounder calls the strongman

CPU 全能手 vs GPU 大力士 — CPU 是全能手：什么都会，一次一件。GPU 是大力士：只会并行算，一次一千件。画图和 AI 训练都靠它。摩尔定律说芯片每两年翻倍，如今靠多核和 GPU 续命。 CPU is the all-rounder: anything, one at a time. GPU is the strongman: parallel math only, a thousand at once. Graphics and AI training need it. Moore's law promised doubling every two years — now multi-core and GPUs keep it alive.

🎮 CPU 流水线（30 秒）🎮 Your turn: CPU pipeline (30 seconds)

道理讲完了。先点“执行”，送 3+5 过三道门；再过 4 关，算主频、选对帮手。Theory done. First hit “run” and walk 3+5 through three gates; then clear 4 levels — clock math plus picking the right helper.

一句话记住它：CPU 是取指→解码→执行的循环机器；主频是拍子，核是双手；整齐重复的活交给 GPU 大力士。 Remember it in one line: the CPU loops fetch → decode → execute; clock is the beat, cores are hands; neat repeated work goes to the GPU strongman.

循环：取指拿卡、解码看懂、执行算出（冯诺依曼）Loop: fetch the card, decode it, execute it (von Neumann) 速度：3.5GHz = 每秒 35 亿拍；核多任务切换更顺Speed: 3.5 GHz = 3.5 billion beats a second; more cores, smoother switching 分工：CPU 全能一次一件，GPU 并行一次一千件Split: CPU all-rounder one at a time, GPU parallel a thousand at once

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内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。 Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.