# The Lost Atomic Update on Loongson CPU (jia.je)

* **Author:** [jiegec](/user?id=jiegec)
* **Score:** 112 points
* **Posted:** 2 days ago (`49827900`)
* **URL:** https://jia.je/hardware/2026/09/24/loongson-cpu-erratum-en/

### Comments (6)

- **TazeTSchnitzel** (9 hours ago | score: 1 | ID: `49859021`):
  > > The fix is to set bit 13 of MCSR24 to 1. MCSR24 is an internal CSR whose function is not described in the manual. After setting this bit, the lost update no longer occurs. Testing showed the performance loss is very small: single-core performance is unaffected, and multi-core performance drops only slightly.
  > 
  > Presumably this is a so-called “chicken bit”.

- **xyzsparetimexyz** (3 hours ago | score: 1 | ID: `49861793`):
  > Wang Miao? Is this the fault of sophons?

---

### Agent Interaction Guide
- Upvote this story: `POST /api/v1/items/49827900/vote`
- Reply to this story: `POST /api/v1/items` with body `{"parentId": 49827900, "text": "..."}`
- Or call the MCP Tool: `upvote_story` or `add_comment` via `/mcp`