Loongson 3A6000: A Star Among Chinese CPUs

Original Article ↗ Hacker News Discussion ↗

China’s new Loongson 3A6000 CPU, based on the domestic LoongArch ISA, is drawing attention for achieving performance roughly between AMD’s first‑generation Zen and Zen 2 chips, despite being limited to four cores and older fabrication nodes. Commenters see it as proof of China’s growing design competence but stress that access to advanced manufacturing equipment and the broader US‑China tech war will determine how far and how fast it can advance. Others highlight the strategic and moral implications of export controls, noting that sanctions may be accelerating China’s push for self‑reliance in semiconductors and open-source software, including Linux-based desktop ecosystems.

Performance and Technical Characteristics

  • 3A6000 is described as Loongson’s best CPU so far, roughly between AMD Zen (14–12 nm) and Zen 2 (7 nm) per core, but limited to 4 cores.
  • Some argue that for most everyday workloads, being in the right order of magnitude of performance matters more than 10–30% deltas.
  • Others stress that “only 4 cores” is a major limitation versus Zen 2’s up to 64 cores, implying big gaps in high‑end and server scenarios.
  • Fabrication is seen as the main chokepoint: China lags in advanced nodes and lithography equipment, though SMIC is reported to be shipping 7 nm parts (e.g., Huawei phones, AI accelerators).

ISA, Architecture, and RISC‑V

  • Loongson now uses its own LoongArch ISA, derived from MIPS but modernized (no delay slots, no HI/LO, etc.).
  • SIMD extensions (LSX, LASX) resemble and extend earlier MIPS vector extensions.
  • The chip includes undocumented extensions to speed up binary-translated x86, ARM, and RISC‑V code.
  • Some commenters suggest Loongson should have gone with RISC‑V; others note RISC‑V wasn’t mature enough when LoongArch was defined, and its vector ecosystem is currently fragmented.

Software, OS, and Open Source

  • Linux support is advancing quickly; LoongArch changes for Linux, GCC, LLVM, and binutils are largely upstreamed.
  • Kernel drivers for the platform are mostly open source; one GPU driver is still out‑of‑tree, but available on GitHub, with only a closed‑source Mesa userspace component.
  • Windows support is considered unlikely, so Linux is seen as the natural desktop and server OS in China for this ISA.
  • Several point out that Chinese companies and academia are very active in open source (including RISC‑V projects) despite Western perceptions.

Geopolitics, Sanctions, and Strategy

  • Large subthread debates whether US chip sanctions are a strategic blunder or necessary containment.
  • One view: sanctions accelerate Chinese self‑reliance, destroy the “buy foreign, don’t build” mentality, and catalyze domestic ecosystems across chips, tools, and AI.
  • Counter‑view: even if China eventually catches up, delaying it 5–10 years is worthwhile for the US and allies.
  • Many frame this as part of a broader “tech war” and de‑globalization; opinions diverge sharply on long‑term outcomes.

Economics, Demographics, and Long‑Term Outlook

  • Some predict China will face a prolonged economic slump, property bust, and severe demographic issues that limit its ability to fund cutting‑edge fabs.
  • Others note that “China collapse” narratives have been repeated for decades and emphasize its large market, human capital, and existing R&D base.
  • There is broad agreement that design capability is strong in China; manufacturing equipment and advanced fabs remain the main constraint.