ASUS C302CA 安装 Linux

本文 ID:0e56cc60-06b8-11ea-b5cc-3d51f7356847

最近在咸鱼上淘到了一个二手的华硕 Chromebook(具体型号是 ASUS C302CA)。四核 M3-6Y30 + 8G 运行内存 + 32G eMMC 存储 + 12.5 寸触摸屏,虽然机身有少量磕碰,笔记本的转折铰链也有问题,但 800 元的价格着实实惠。

机器寄过来的时候依然是原装系统(Power Wash 过的 Chrome OS)。写个文章记录一将 OS 从 Chrome OS 换成 elementary OS 的过程。


Chromebook 的 BIOS 都是为了配合 Chrome OS 而特殊定做的,因此无法用来启动其他操作系统,没有 BIOS 设置界面,也无法升级 BIOS。但是可能是出于修理和防止可能的 BIOS 紧急固件更新,制造商仍然允许使用者解除 BIOS 的写入保护。常见的保护方式在 Chromium Projects Wiki 里有详细说明:

Application Processor (AP) Firmware

AP firmware (also known as “SOC firmware”, “host firmware”, “main firmware” or even “BIOS”) typically resides on a SPI ROM. Protection registers on the SPI ROM are programmed to protect the read-only region, and these registers normally cannot be modified while the SPI ROM WP (write protect) pin is asserted. This pin is asserted through various physical means (see below), but with effort, users can unprotect devices they own.

Embedded Controller (EC) Firmware

The Chrome OS Embedded Controller (EC) typically has a WP input pin driven by the same hardware that generates SOC firmware write protect. While this pin is asserted, certain debug features (eg. arbitrary I2C access through host commands) are locked out. Some ECs load code from external storage, and for these ECs, RO protection works similar to SOC firmware RO protection (WP pin is asserted to EC SPI ROM). Other ECs use internal flash, and these ECs emulate SPI ROM protection registers, disabling write access to certain regions while the WP pin is asserted.

解除写保护的操作在 Wiki 里同样有说明:

Methods of Asserting Write Protect

Throughout the history of Chrome OS devices, three main methods have been implemented for asserting (and removing) write protect:

  • Switch - a toggle switch asserts WP to the SOC firmware SPI ROM and EC. WP can be deasserted by disassembling the device and flipping the switch.
  • Screw - a screw shorts a pad on the PCB. While this screw is inserted, WP is asserted. WP can be deasserted by disassembling the device and removing this special screw.
  • cr50 - a special security chip asserts the WP signal. While a battery is present on the device, the WP signal will be asserted. Disassembling the device and physically disconnecting the battery causes WP to be deasserted.

More information about which protection method is used for a particular device, and where to locate the switch / screw, is available on the developer info page.

ASUS C302CA 这个型号的超极本使用的是”Screw(螺丝)“方法,因此我们需要拆开后盖,拧下主板上的 BIOS 写保护螺丝。注意在拆卸背板的时候,有两颗螺丝藏在上侧脚垫下,需要先用工具去除脚垫再拆卸这两颗螺丝。下侧的两个脚垫下没有螺丝。如图所示,图片来源请 点击此处

随后移除后盖,就能看到主板和电池。在主板上由小条黑布覆盖的螺丝即为写保护螺丝,小心拧下即可。位置见下图白色圈内,图片来源请 点击此处

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